U.S. patent application number 11/686435 was filed with the patent office on 2007-10-04 for automatic transmission control system.
This patent application is currently assigned to JATCO Ltd.. Invention is credited to Yukiyoshi INUTA, Kenichi KAIZU, Hiroki KUMASHIRO, Hiroshi SEKIGUCHI, Hideharu YAMAMOTO.
Application Number | 20070232445 11/686435 |
Document ID | / |
Family ID | 38267720 |
Filed Date | 2007-10-04 |
United States Patent
Application |
20070232445 |
Kind Code |
A1 |
YAMAMOTO; Hideharu ; et
al. |
October 4, 2007 |
AUTOMATIC TRANSMISSION CONTROL SYSTEM
Abstract
An automatic transmissions control system varies times to start
a shift to securing a good response in engagement pressure for an
engagement-side frictional element as well as suppressing
occurrence of hydraulic pressure vibrations at low temperatures.
The control system has an engagement pressure at-low-temperature
regulation section that selectively controls at least one of the
first and second engagement-pressure regulator valves, when the oil
temperature is detected to be lower than a predetermined oil
temperature and the shift condition is determined to exist
requiring a shift operation such that the first engagement-pressure
regulator valve provides a maximum hydraulic pressure to engage the
first frictional element to start a shift with the maximum
hydraulic pressure being continuously provided until the shift
ends, and/or the second engagement-pressure regulator valve
provides a minimum hydraulic pressure to obtain complete
disengagement of the second frictional element to start a downshift
as the shift operation.
Inventors: |
YAMAMOTO; Hideharu;
(Fujinomiya-shi, JP) ; KAIZU; Kenichi; (Fuji-shi,
JP) ; SEKIGUCHI; Hiroshi; (Fuji-shi, JP) ;
INUTA; Yukiyoshi; (Sagamihara-shi, JP) ; KUMASHIRO;
Hiroki; (Fuji-shi, JP) |
Correspondence
Address: |
GLOBAL IP COUNSELORS, LLP
1233 20TH STREET, NW, SUITE 700
WASHINGTON
DC
20036-2680
US
|
Assignee: |
JATCO Ltd.
Fuji-shi
JP
|
Family ID: |
38267720 |
Appl. No.: |
11/686435 |
Filed: |
March 15, 2007 |
Current U.S.
Class: |
477/98 |
Current CPC
Class: |
F16H 2200/0052 20130101;
F16H 2306/52 20130101; F16H 3/66 20130101; F16H 61/061 20130101;
F16H 2200/201 20130101; F16H 59/72 20130101; F16H 2306/44 20130101;
Y10T 477/653 20150115; F16H 61/686 20130101 |
Class at
Publication: |
477/98 |
International
Class: |
F16H 59/00 20060101
F16H059/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 30, 2006 |
JP |
2006-092804 |
Claims
1. An automatic transmission control system comprising: a shift
determination section configured to determine an existence of a
shift condition that requires a shift operation in an automatic
transmission including at least first and second frictional
elements that performs the shift operation by selective engagement
of the first frictional element and selective disengagement of the
second frictional element; a shift control section configured to
selectively control a line pressure regulator valve that regulates
line pressure by draining ejection pressure of an oil pump and
first and second engagement-pressure pressure regulator valves that
regulate line pressure to provide engagement pressure to the first
and second frictional elements; an oil temperature detection
section configured to detect oil temperature within the automatic
transmission; and an engagement pressure at-low-temperature
regulation section configured to selectively control at least one
of the first and second engagement-pressure regulator valves, when
the oil temperature detected by the oil temperature detection
section is lower than a predetermined oil temperature and the shift
determination section determines the existence of the shift
condition for requiring the shift operation such that either the
first engagement-pressure regulator valve provides a maximum
hydraulic pressure to engage the first frictional element to start
a shift with the maximum hydraulic pressure being continuously
provided until the shift ends, or the second engagement-pressure
regulator valve provides a minimum hydraulic pressure to obtain
complete disengagement of the second frictional element to start a
downshift as the shift operation and the first engagement-pressure
regulator valve provides a maximum hydraulic pressure to obtain
complete engagement of the first frictional element upon elapse of
a predetermined period from the start of the downshift with the
maximum hydraulic pressure being continuously provided until the
downshift ends.
2. The automatic transmission control system as recited in claim 1,
wherein the engagement pressure at-low-temperature regulation
section is further configured to control the second
engagement-pressure regulator valve to the minimum hydraulic
pressure upon elapse of a predetermined period from starting an
upshift as the shift operation, upon the oil temperature detection
section detecting the oil temperature is lower than the
predetermined oil temperature and the shift determination section
determining an existence of an upshift condition for requiring the
upshift, when the engagement pressure at-low-temperature regulation
section is controlling the first engagement-pressure regulator
valve to continuously provide the maximum hydraulic pressure to
engage the first frictional element until the upshift ends.
3. The automatic transmission control system as recited in claim 1,
wherein the engagement pressure at-low-temperature regulation
section is configured to control the second engagement-pressure
regulator valve to provide the minimum hydraulic pressure to obtain
complete disengagement of the second frictional element to start
the downshift and the first engagement-pressure regulator valve
provides the maximum hydraulic pressure to obtain complete
engagement of the first frictional element upon elapse of the
predetermined period from the start of the downshift with the
maximum hydraulic pressure being continuously provided until the
downshift ends.
4. The automatic transmission control system as recited in claim 1,
further comprising a line pressure at-low-temperature regulation
section configured to control the line pressure regulator valve
based on an input torque to the automatic transmission for a
predetermined period from starting the shift operation so that line
pressure is as high as a lower limit hydraulic pressure required to
end an inertia phase, upon the oil temperature detection section
detecting the oil temperature is lower than a predetermined oil
temperature and the shift determination section determining the
existence of the shift condition.
5. The automatic transmission control system as recited in claim 2,
further comprising a line pressure at-low-temperature regulation
section configured to control the line pressure regulator valve
based on an input torque to the automatic transmission for a
predetermined period from starting the shift operation so that line
pressure is as high as a lower limit hydraulic pressure required to
end an inertia phase, upon the oil temperature detection section
detecting the oil temperature is lower than a predetermined oil
temperature and the shift determination section determining the
existence of the shift condition.
6. The automatic transmission control system as recited in claim 3,
further comprising a line pressure at-low-temperature regulation
section configured to control the line pressure regulator valve
based on an input torque to the automatic transmission for a
predetermined period from starting the shift operation so that line
pressure is as high as a lower limit hydraulic pressure required to
end an inertia phase, upon the oil temperature detection section
detecting the oil temperature is lower than a predetermined oil
temperature and the shift determination section determining the
existence of the shift condition.
7. The automatic transmission control system as recited in claim 1,
further comprising a line pressure at-low-temperature regulation
section configured to control the line pressure regulator valve for
a predetermined period from starting the shift operation, upon the
oil temperature detection section detecting the oil temperature is
lower than a predetermined oil temperature and the shift
determination section determining the existence of the shift
condition, such that the line pressure regulator valve provides a
hydraulic pressure that is lower than the line pressure that is
used when the oil temperature detected by the oil temperature
detection section is equal to or higher than the predetermined oil
temperature and the shift determination section determine
determines the existence of the shift condition.
8. The automatic transmission control system as recited in claim 2,
further comprising a line pressure at-low-temperature regulation
section configured to control the line pressure regulator valve for
a predetermined period from starting the shift operation, upon the
oil temperature detection section detecting the oil temperature is
lower than a predetermined oil temperature and the shift
determination section determining the existence of the shift
condition, such that the line pressure regulator valve provides a
hydraulic pressure that is lower than the line pressure that is
used when the oil temperature detected by the oil temperature
detection section is equal to or higher than the predetermined oil
temperature and the shift determination section determine
determines the existence of the shift condition.
9. The automatic transmission control system as recited in claim 3,
further comprising a line pressure at-low-temperature regulation
section configured to control the line pressure regulator valve for
a predetermined period from starting the shift operation, upon the
oil temperature detection section detecting the oil temperature is
lower than a predetermined oil temperature and the shift
determination section determining the existence of the shift
condition, such that the line pressure regulator valve provides a
hydraulic pressure that is lower than the line pressure that is
used when the oil temperature detected by the oil temperature
detection section is equal to or higher than the predetermined oil
temperature and the shift determination section determine
determines the existence of the shift condition.
10. The automatic transmission control system as recited in claim
1, wherein the shift determination section is further configured to
a detect a lever operation from a non-run range to a run range for
engaging the first frictional element as the shift condition
requiring the shift operation; and the engagement pressure
at-low-temperature regulation section is configured to control the
first engagement-pressure regulator valve to provide the maximum
hydraulic pressure to obtain complete engagement of the first
friction element to start the shift, with the maximum hydraulic
pressure being continuously provided until the shift ends, upon the
oil temperature detection section detecting the oil temperature is
lower than the predetermined oil temperature and the shift
determination section determining an existence of the lever
operation as the shift condition for requiring the shift.
11. The automatic transmission control system as recited in claim
10, further comprising a line pressure at-low-temperature
regulation section configured to control the line pressure
regulator valve based on an input torque to the automatic
transmission for a predetermined period from starting the shift
operation so that line pressure is as high as a lower limit
hydraulic pressure required to end an inertia phase, upon the oil
temperature detection section detecting the oil temperature is
lower than a predetermined oil temperature and the shift
determination section determining the existence of the shift
condition.
12. The automatic transmission control system as recited in claim
10, further comprising a line pressure at-low-temperature
regulation section configured to control the line pressure
regulator valve for a predetermined period from starting the shift
operation, upon the oil temperature detection section detecting the
oil temperature is lower than a predetermined oil temperature and
the shift determination section determining the existence of the
shift condition, such that the line pressure regulator valve
provides a hydraulic pressure that is lower than the line pressure
that is used when the oil temperature detected by the oil
temperature detection section is equal to or higher than the
predetermined oil temperature and the shift determination section
determine determines the existence of the shift condition.
13. An automatic transmission control system comprising: shift
determination means for determining an existence of a shift
condition that requires a shift operation in an automatic
transmission including at least first and second frictional
elements that performs the shift operation by selective engagement
of the first frictional element and selective disengagement of the
second frictional element; shift control means for selectively
controlling a line pressure regulator valve that regulates line
pressure by draining ejection pressure of an oil pump and first and
second engagement-pressure pressure regulator valves that regulate
line pressure to provide engagement pressure to the first and
second frictional elements; oil temperature detection means for
detecting oil temperature within the automatic transmission; and
engagement pressure at-low-temperature regulation means for
selectively controlling at least one of the first and second
engagement-pressure regulator valves, when the oil temperature that
was detected is lower than a predetermined oil temperature and the
shift condition for requiring the shift operation was determined to
exist such that either the first engagement-pressure regulator
valve provides a maximum hydraulic pressure to engage the first
frictional element to start a shift with the maximum hydraulic
pressure being continuously provided until the shift ends, or the
second engagement-pressure regulator valve provides a minimum
hydraulic pressure to obtain complete disengagement of the second
frictional element to start a downshift as the shift operation and
the first engagement-pressure regulator valve provides a maximum
hydraulic pressure to obtain complete engagement of the first
frictional element upon elapse of a predetermined period from the
start of the downshift with the maximum hydraulic pressure being
continuously provided until the downshift ends.
14. An automatic transmission control method comprising:
determining an existence of a shift condition that requires a shift
operation in an automatic transmission including at least first and
second frictional elements that performs the shift operation by
selective engagement of the first frictional element and selective
disengagement of the second frictional element; selectively
controlling a line pressure regulator valve that regulates line
pressure by draining ejection pressure of an oil pump and first and
second engagement-pressure pressure regulator valves that regulate
line pressure to provide engagement pressure to the first and
second frictional elements; detecting oil temperature within the
automatic transmission; and selectively controlling at least one of
the first and second engagement-pressure regulator valves, when the
oil temperature that was detected is lower than a predetermined oil
temperature and the shift condition for requiring the shift
operation was determined to exist such that either the first
engagement-pressure regulator valve provides a maximum hydraulic
pressure to engage the first frictional element to start a shift
with the maximum hydraulic pressure being continuously provided
until the shift ends, or the second engagement-pressure regulator
valve provides a minimum hydraulic pressure to obtain complete
disengagement of the second frictional element to start a downshift
as the shift operation and the first engagement-pressure regulator
valve provides a maximum hydraulic pressure to obtain complete
engagement of the first frictional element upon elapse of a
predetermined period from the start of the downshift with the
maximum hydraulic pressure being continuously provided until the
downshift ends.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to Japanese Patent
Application No. 2006-092804, filed on Mar. 30, 2006. The entire
disclosure of Japanese Patent Application No. 2006-092804 is hereby
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention generally relates to control systems
for automatic transmissions. More specifically, the present
invention relates to an automatic transmission control system that
controls the hydraulic pressure in an automatic transmission during
shifting at low temperatures.
[0004] 2. Background Information
[0005] Automatic transmissions have been proposed in which
hydraulic pressure is controlled at low temperatures during
shifting to avoid shift shock. For example, Japanese Patent
Application Laid-Open Publication No. 10-103483A discloses an
automatic transmission that uses such hydraulic pressure control at
low temperatures during shifting to avoid shift shock. In
particular, because the fluidity of automatic transmission
hydraulic fluid drops at low temperatures, the response
characteristics of hydraulic pressure supplied to frictional
elements (e.g., clutches, brakes, etc.) are reduced and shift shock
occur. In view of this situation, the conventional technology
described in this above-mentioned patent publication proposes to
determine an end timing of a so-called precharge control based on a
rate of change of turbine rotational speed in order to avoid
occurrence of rapid engagement shocks.
[0006] In view of the above, it will be apparent to those skilled
in the art from this disclosure that there exists a need for an
improved automatic transmission control system. This invention
addresses this need in the art as well as other needs, which will
become apparent to those skilled in the art from this
disclosure.
SUMMARY OF THE INVENTION
[0007] It has been discovered that in the above-mentioned
conventional technology, there are several potential problems.
First, as taught by the conventional technology, oil pressure
vibrations (abbreviated hereinafter as "oil vibrations") occur when
a pressure regulator valve for a clutch is operated greatly at low
temperatures, for example, equal to or less than -20.degree. C.,
where the automatic transmission oil has an extremely high
viscosity, in the same manner as at normal temperatures by
supplying an oil pressure (a high pressure state) from a zero oil
pressure (a low pressure state), and then subsequently supplying a
maintenance oil pressure (a low pressure state) and supplying an
oil pressure for progress of inertia phase (a high pressure state).
Thus, at low temperatures when the response characteristics of oil
pressure reduce, there is a possibility of loosing control of such
oil vibrations once they occur.
[0008] Second, at low temperatures, for example, equal to or less
than -20.degree. C., where the automatic transmission oil has an
extremely high viscosity, there is another problem that time taken
for oil pressure to rise varies greatly in addition to the
reduction in the response characteristics of oil pressure.
[0009] The present invention was contrived in view of the foregoing
drawbacks in the above mentioned conventional control system for an
automatic transmission. One object of the present invention is to
provide a control system for automatic transmissions, which can
control the variations of time until the beginning of engagement
while securing at least the response characteristics of engagement
pressure to the engagement side of a frictional element at low
temperatures and control the occurrence of oil pressure
variations.
[0010] In order to achieve the above mentioned object and other
objects of the present invention, an automatic transmission control
system is provided that basically comprises a shift determination
section, a shift control section, an oil temperature detection
section, an oil temperature detection section and an engagement
pressure at-low-temperature regulation section. The shift
determination section is configured to determine an existence of a
shift condition that requires the shift operation in an automatic
transmission including at least first and second frictional
elements that performs a shift operation by selective engagement of
the first frictional element and selective disengagement of the
second frictional element. The shift control section is configured
to selectively control a line pressure regulator valve that
regulates line pressure by draining ejection pressure of an oil
pump and first and second engagement-pressure pressure regulator
valves that regulate line pressure to provide engagement pressure
to the first and second frictional elements. The oil temperature
detection section is configured to detect oil temperature within
the automatic transmission. The engagement pressure
at-low-temperature regulation section is configured to selectively
control at least one of the first and second engagement-pressure
regulator valves, when the oil temperature detected by the oil
temperature detection section is lower than a predetermined oil
temperature and the shift determination section determines the
existence of the shift condition for requiring the shift operation
such that either the first engagement-pressure regulator valve
provides a maximum hydraulic pressure to engage the first
frictional element to start a shift with the maximum hydraulic
pressure being continuously provided until the shift ends, or the
second engagement-pressure regulator valve provides a minimum
hydraulic pressure to obtain complete disengagement of the second
frictional element to start a downshift as the shift operation and
the first engagement-pressure regulator valve provides a maximum
hydraulic pressure to obtain complete engagement of the first
frictional element upon elapse of a predetermined period from the
start of the downshift with the maximum hydraulic pressure being
continuously provided until the downshift ends.
[0011] These and other objects, features, aspects and advantages of
the present invention will become apparent to those skilled in the
art from the following detailed description, which, taken in
conjunction with the annexed drawings, discloses a preferred
embodiment of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Referring now to the attached drawings which form a part of
this original disclosure:
[0013] FIG. 1 is a simplified schematic view (skeleton diagram) of
an automatic transmission with six (6) forward gears and one (1)
reverse gear that can be achieved by an automatic transmission
control system in accordance with a first embodiment of the present
invention;
[0014] FIG. 2 is a frictional element engagement operating chart
showing the state of operation of each of frictional elements in
each of shift stages that are established by the automatic
transmission control system in accordance with the first embodiment
of the present invention;
[0015] FIG. 3 is a diagrammatic view of a hydraulic circuit and an
electronic shift control system in accordance with the first
embodiment of the present invention;
[0016] FIG. 4 is an axial direction section of a pressure regulator
valve for engagement pressure applied to a frictional element in
accordance with the first embodiment of the present invention;
[0017] FIG. 5 is an axial direction section of a pressure regulator
valve for engagement pressure applied to a frictional element in
accordance with the first embodiment of the present invention;
[0018] FIG. 6 is an axial direction section of a line pressure
regulator valve in accordance with the first embodiment of the
present invention;
[0019] FIG. 7 is an axial direction section of a line pressure
regulator valve in accordance with the first embodiment of the
present invention;
[0020] FIG. 8 is an axial direction section of a line pressure
regulator valve in accordance with the first embodiment of the
present invention;
[0021] FIG. 9 is a block diagram showing the constitution of
functions of a major portion of the automatic transmission control
system in accordance with the first embodiment of the present
invention;
[0022] FIG. 10 shows line pressure maps stored in the automatic
transmission control system in accordance with the first embodiment
of the present invention;
[0023] FIG. 11 is a time chart showing the hydraulic characteristic
at the time of a normal downshift by the automatic transmission
control system in accordance with the first embodiment of the
present invention;
[0024] FIG. 12 is a flow chart showing the operation at the time of
the normal downshift by the automatic transmission control system
in accordance with the first embodiment of the present
invention;
[0025] FIG. 13 is a time chart showing the hydraulic pressure
characteristic at the time of normal upshift by the automatic
transmission control system in accordance with the first embodiment
of the present invention;
[0026] FIG. 14 is a flow chart showing the operation at the time of
normal upshift by the automatic transmission control system in
accordance with the first embodiment of the present invention;
[0027] FIG. 15 is a time chart showing the hydraulic pressure
characteristic at the time of normal select by the automatic
transmission control system in accordance with the first embodiment
of the present invention;
[0028] FIG. 16 is a flow chart showing the operation at the time of
normal select by the automatic transmission control system in
accordance with the first embodiment of the present invention;
[0029] FIG. 17 is a time chart showing the processing steps at the
beginning of inertia-phase control at the time of normal select by
the automatic transmission control system in accordance with the
first embodiment of the present invention;
[0030] FIG. 18 is a flow chart showing the operation at the time of
low temperature downshift the automatic transmission control system
in accordance with the first embodiment of the present
invention;
[0031] FIG. 19 is a time chart showing the hydraulic pressure
characteristic at the time of low temperature downshift by the
first embodiment of a control system for an automatic
transmission;
[0032] FIG. 20 is a flow chart showing the operation at the time of
low temperature upshift the automatic transmission control system
in accordance with the first embodiment of the present
invention;
[0033] FIG. 21 is a time chart showing the hydraulic pressure
characteristic at the time of low upshift the automatic
transmission control system in accordance with the first embodiment
of the present invention;
[0034] FIG. 22 is a flow chart showing the operation at the time of
low temperature select the automatic transmission control system in
accordance with the first embodiment of the present invention;
and
[0035] FIG. 23 is a time chart showing the hydraulic pressure
characteristic at the time of low temperature select the automatic
transmission control system in accordance with the first embodiment
of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] Selected embodiments of the present invention will now be
explained with reference to the drawings. It will be apparent to
those skilled in the art from this disclosure that the following
descriptions of the embodiments of the present invention are
provided for illustration only and not for the purpose of limiting
the invention as defined by the appended claims and their
equivalents.
[0037] Referring initially to FIG. 1, an automatic transmission 1
is illustrated in accordance with a first embodiment of the present
invention. FIG. 1 is a simplified schematic view (skeleton diagram)
of the automatic transmission 1 having six (6) forward gears and
one (1) reverse gear that can be achieved by an automatic
transmission control system in accordance with a first embodiment
of the present invention. As shown in FIG. 1, the automatic
transmission 1 receives power of an engine 2. In particular, the
rotational output of the engine 2 is fed to a torque converter 3 of
the automatic transmission 1. The rotational output of the torque
converter 3 is fed to a double-pinion type planetary gear mechanism
4 via a rotary shaft S1.
[0038] Here, the double-pinion type planetary gear mechanism 4 is
disposed in a transmission case 6 of the automatic transmission 1.
The double-pinion type planetary gear mechanism 4 basically
includes a carrier 5, a sun gear 7, a plurality of inner diameter
side pinion gears 8, a plurality of outer diameter side pinion
gears 9, and a ring gear 10. The rotational output of the torque
converter 3 is fed to the carrier 5 via the rotary shaft S1.
[0039] The sun gear 7 is fixed to the transmission case 6. The
inner diameter side pinion gears 8 mesh with the sun gear 7. The
outer diameter side pinion gears 9 mesh with the inner diameter
side pinion gears 8. The ring gear 10 meshes with the outer
diameter side pinion gears 9 and is arranged coaxially with the sun
gear 7. The carrier 5 supports the inner diameter side pinion gears
8 and the outer diameter side pinion gears 9 for rotation about
their axes.
[0040] The ring gear 10 is connected to a rotary shaft S2 that
extends toward the side of the engine 2 after passing through an
area surrounded by an inner diameter side of an output gear 17 that
covers the periphery of a rotary shaft S1 mentioned later.
[0041] Again, the carrier 5 is connected via a high clutch H/C to a
rotary shaft S3 that covers the periphery of the rotary shaft S2
and extends toward the side of the engine 2.
[0042] That end portion of the rotary shaft S3 which is on the side
opposite to the side where the high clutch H/C is connected to the
rotary shaft S3 is connected to a carrier 16 that supports pinion
gears 13 of a single pinion type planetary mechanism 11. The
carrier 16 is connected to the transmission case 6 via a low &
reverse brake L&R/B and a low one-way clutch LOW/OWC arranged
in parallel. By this parallel arrangement, the carrier 16 is
supported with respect to the transmission case 6 for rotation in
one direction and its rotation can be regulated (fixed) or
deregulated.
[0043] The single pinion type planetary gear mechanism 11 is formed
by the pinion gears 13 which mesh not only with a second sun gear
14 disposed on the side of the engine 2 and with a first sun gear
12 disposed on the side opposite to the side of the engine 2 but
also with a ring gear 15.
[0044] The first sun gear 12 is connected to a rotary shaft S4 that
extends in a direction opposite to the direction toward the engine
2 and covers the periphery of the rotary shaft S3, and the rotary
shaft S4 is connected to the transmission case 6 via a 2-6 brake
2-6/B. By this arrangement, the rotary shaft S4 can be fixedly
connected to or disconnected from the transmission case 6.
[0045] The second sun gear 14 is connected to a rotary shaft S5
that extends past the inner diameter side of an output gear 17
toward the side of the engine 2 and covers the periphery of the
rotary shaft S2, and the rotary shaft S5 is connectable to the
rotary shaft S2 via a 3-5 reverse clutch 3-5R/C and it is
connectable to a ring gear 21 of a single pinion type planetary
gear mechanism 18 via a low clutch LOW/C.
[0046] Here, the single pinion type planetary gear mechanism 18 is
disposed around the periphery side of the rotary shaft S5 and
between the output gear 17 and a 3-5 reverse clutch 3-5R/C. The
single pinion type planetary gear mechanism 18 includes a sun gear
19 connected to the rotary shaft S5, a ring gear 21 disposed around
the outer diameter side of the sun gear 19, and a plurality of
pinion gears 20 meshing with the sun gear 19 and the ring gear 21.
The pinion gears 20 are supported by a carrier 22.
[0047] The carrier 22 is connected to the ring gear 15 of the
single pinion type planetary gear mechanism 11 via a rotary shaft
S6 that covers the periphery side of the rotary shaft S5 and passes
through an area on the inner diameter side of the output gear
17.
[0048] Between the single pinion type planetary gear mechanism 11
and the single pinion type planetary gear mechanism 18 is arranged
a bearing support portion 30. The bearing support portion 30 is a
partition shaped part that is integral with the transmission case 6
and has a bearing carrier portion 31 that is of a cylinder
extending along the rotary shaft S6.
[0049] Bearings 32 are fitted on the periphery of the bearing
carrier portion 31, and the output gear 17 connected to the ring
gear 15 is contact with the peripheral portion (an outer race) of
the bearings 32. On the inner diameter side of the bearing carrier
portion 31, a pile of the coaxial rotary shafts S2, S2, S5 and S6
forms a multiplex structure.
[0050] And, the automatic transmission 1 performs automatic shift
control among six forward gears at a D range position based on a
driving point, which determined by vehicle speed and throttle
opening degree, and a shift schedule (a shift map), and shift
control to a reverse first gear by operation to select a R range
position from the D range position.
[0051] In this case, selecting one of various combinations of
engagement and disengagement of the high clutch H/C, the 2-6 brake
2-6/B, the low & reverse brake L&R/B (low one-way clutch
LOW/OWC), the low clutch LOW/C, and the 3-5 reverse clutch 3-5R/C
causes the automatic transmission 1 to change an output rpm of the
engine 2 to a desired rpm, which is transmitted from the output
gear 17 to a drive wheel of the vehicle (not illustrated) via the
counter shaft 23 and the differential gear 24.
[0052] FIG. 2 shows the operation state of each of the frictional
elements in this shift control. In FIG. 2, a circle mark
.largecircle. represents engagement, no mark represents
disengagement, an encircled X mark {circle around (X)} represents
engagement but operating at the time of engine braking, and a
shadowed circle mark with hatching represents mechanical engagement
(regulation of rotation) operating at the time of engine
driving.
[0053] First gear (1.sup.st) is achieved by engaging the low clutch
LOW/C and engaging the low & reverse brake L&R/B or the low
one-way clutch LOW/OWC. At the D range position, a rotation
received from the input shaft (rotary shaft S1) and reduced via the
double pinion type planetary gear mechanism 4 is delivered from the
rotary shaft S2 via the engaged low clutch LOW/C and the ring gear
21 of the single pinion type planetary gear mechanism 18 to the
carrier 22. The rotation of the carrier 22 is transmitted to the
ring gear 15, but the rotation of the ring gear 15 is reduced
because the carrier 16 that is fixed to the transmission case 6 by
the engagement of the low one-way clutch LOW/OWC receives a
reaction force, with the result that a rotation reduced at the
maximum reduction ratio is outputted from the output gear 17. In
addition, at the time of engine braking, the low & reverse
brake L&R/B receives a reaction force instead of the racing low
one-way clutch LOW/OWC.
[0054] Second gear (2.sup.nd) is achieved by engaging the low
clutch LOW/C and 2-6 brake 2-6/B. In the second gear, a rotation
received from the input shaft (rotary shaft S1) and reduced via the
double pinion type planetary gear mechanism 4 is delivered from the
rotary shaft S2 via the engaged low clutch LOW/C and the ring gear
21 of the single pinion type planetary gear mechanism 18 to the
carrier 22. On one hand, the first sun gear 12 and pinion gears 13
are fixed to the transmission case 6 by the 2-6 brake 2-6/B. In
addition, the rotary shaft S5 connected to the second sun gear 14
is fixed to the transmission case 6 because the pinion gears 13
mesh with the second sun gear 14.
[0055] Third gear (3.sup.rd) is obtained by engaging the 3-5
reverse clutch 3-5R/C and the low clutch LOW/C, fourth gear
(4.sup.th) is obtained by engaging the high clutch H/C and low
clutch LOW/C. In addition, fifth gear (5.sup.th) is obtained by
engaging the high clutch H/C and the 3-5 reverse clutch 3-5R/C.
[0056] Sixth gear (6.sup.th) is obtained by engaging the high
clutch H/C and the 2-6 brake 2-6/B. In addition, in the sixth gear,
the rotary shaft S5 is fixed by engaging the 2-6 brake 2-6/B
similarly to the second gear. In addition, the reverse gear (REV)
is obtained by engaging the 3-5 reverse clutch 3-5R/C and the low
& reverse brake L&R/B.
[0057] Hydraulic Circuit and Electronic Shift Control System
[0058] Next, referring to FIG. 3, there is description on the
hydraulic circuit and electronic shift control system which
accomplish the above-mentioned shift control. In FIG. 3, the
hydraulic circuit is provided with an engagement piston chamber 101
of the low clutch LOW/C, an engagement piston chamber 102 of the
high clutch H/C, an engagement piston chamber 103 of the 2-6 brake
2-6/B, an engagement piston chamber 104 of the 3-5 reverse clutch
3-5R/C, and an engagement piston chamber 105 of the low &
reverse brake L&R/B.
[0059] The low clutch LOW/C, the high clutch H/C, the 2-6 brake
2-6/B, the 3-5 reverse clutch 3-5R/C, and the low & reverse
brake L&R/B are engaged when a line pressure PL, a D range
pressure or a R range pressure are supplied to each of their
engagement piston chambers 101.about.105, and disengaged when these
engagement pressures are drained from each of them.
[0060] Further, the D range pressure is the line pressure PL via a
manual valve 116 and occurs only at the time of selection of a D
range. The R range pressure is the line pressure PL via the manual
valve 116 and occurs only at the time of selection of an R range,
and it will not occur at the time of selection of ranges other than
the R range because of connection to a drain port.
[0061] In the hydraulic circuit illustrated in FIG. 3, a first
hydraulic control valve 106 is provided that controls an engagement
pressure (a low clutch pressure) supplied to the low clutch LOW/C.
Also a second hydraulic control valve 107 is provided controls an
engagement pressure (a high clutch pressure) supplied to the high
clutch H/C. Also a third hydraulic control valve 108 is provided
that controls an engagement pressure (a 2-6 brake pressure)
supplied to the 2-6 brake 2-6/B. Also a fourth hydraulic control
valve 109 is provided that controls an engagement pressure (a 3-5
reverse clutch pressure) supplied to the 3-5 reverse clutch 3-5R/C.
Further a fifth hydraulic control valve 110 is provided that
controls an engagement pressure (a low & reverse brake
pressure) supplied to the low & reverse brake L&R/B.
Finally, a line pressure control valve 132 is also provided that
controls the line pressure PL.
[0062] The first hydraulic control valve 106 is composed of a first
duty solenoid 106a and a first pressure regulator valve 106b. The
first duty solenoid 106a produces a solenoid pressure using a pilot
pressure as a base pressure. The first pressure regulator valve
106b, regulates the D range pressure to the low clutch pressure
using the solenoid pressure from the first duty solenoid 106a as an
operation signal pressure and letting this low clutch pressure act
thereon as a feedback pressure. In addition, the first duty
solenoid 106a is controlled depending on a duty ratio, causing, to
be concrete, the first pressure regulator valve 106b to set the low
clutch pressure at zero at the time of solenoid OFF and to raise
the low clutch pressure when the ON duty ratio increases at the
time of solenoid ON.
[0063] The second hydraulic control valve 107 is composed of a
second duty solenoid 107a and a second pressure regulator valve
107b. The second duty solenoid 107a produces a solenoid pressure
using the pilot pressure as a base pressure. The second pressure
regulator valve 107b regulates the D range pressure to the high
clutch pressure using the solenoid pressure from the second duty
solenoid 107a as an operation signal pressure and letting this high
clutch pressure act thereon as a feedback pressure. In addition,
the second duty solenoid 106a causes the second pressure regulator
valve 107b to set the high clutch pressure at zero at the time of
solenoid ON (100% ON duty ratio), to raise the high clutch pressure
when the ON duty ratio decreases, and to maximize the high clutch
pressure at the time of solenoid OFF.
[0064] The third hydraulic control valve 108 is composed of a third
duty solenoid 108a and a third pressure regulator valve 108b. The
third duty solenoid 108a produces a solenoid pressure using the
pilot pressure as a base pressure. The third pressure regulator
valve 108b regulates the D range pressure to the 2-6 brake pressure
using the solenoid pressure from the third duty solenoid 108a as an
operation signal pressure and letting this 2-6 brake pressure act
thereon as a feedback pressure. In addition, the third duty
solenoid 108a causes the third pressure regulator valve 108b to set
the 2-6 brake pressure at zero at the time of solenoid OFF, and to
raise the 2-6 brake pressure when the ON duty ratio increases at
the time of solenoid ON.
[0065] The fourth hydraulic control valve 109 is composed of a
fourth duty solenoid 109a and a fourth pressure regulator valve
109b. The fourth duty solenoid 109a produces a solenoid pressure
using the pilot pressure as a base pressure. The fourth pressure
regulator valve 109b regulates the D range pressure to the 3-5
reverse clutch pressure using the solenoid pressure from the fourth
duty solenoid 108a as an operation signal pressure and letting this
3-5 reverse clutch pressure act thereon as a feedback pressure. In
addition, the fourth pressure regulator valve 109b regulates the R
range pressure to the 3-5 reverse clutch pressure at the time of
selection of the R range. In addition, the fourth duty solenoid
109a causes the fourth pressure regulator valve 109b to set the 3-5
reverse clutch pressure at zero at the time of solenoid ON (100% ON
duty ratio), to raise the 3-5 reverse clutch pressure when the ON
duty ratio decreases, and to maximize the 3-5 reverse clutch
pressure at the time of solenoid OFF.
[0066] By the way, on a supply hydraulic circuit to the fourth
hydraulic control valve 109, there is a shuttle ball 109c that
serves as a ball valve for two-direction change. This shuttle ball
109c changes so as to output only one of the D range pressure and R
range pressure to the fourth hydraulic control valve 109.
[0067] The fifth hydraulic control valve 110 is composed of a fifth
duty solenoid 110a and a fifth pressure regulator valve 110b. The
fifth duty solenoid 110a produces a solenoid pressure using the
pilot pressure as a base pressure. The fifth pressure regulator
valve 110b regulates the line pressure PL to the low & reverse
brake pressure using the solenoid pressure from the fifth duty
solenoid 110a as an operation signal pressure and letting this low
& reverse brake pressure act thereon as a feedback pressure. In
addition, the fifth duty solenoid 110a causes the fifth pressure
regulator valve 110b to set the low & reverse brake pressure at
zero at the time of solenoid OFF, and to raise the low &
reverse brake pressure when the ON duty ratio increases at the time
of solenoid ON.
[0068] The line pressure control valve 132 is composed of a linear
solenoid 132a and a line pressure regulator valve 132b. The linear
solenoid 132a is a three-way proportional electromagnetic valve,
which produces a solenoid pressure using the pilot pressure as a
base pressure. The line pressure regulator valve 132b regulates the
ejection pressure of the oil pump O/P, by draining it, to the line
pressure PL using the solenoid pressure from the linear solenoid
132a as an operation signal pressure and letting this line pressure
act thereon as a feedback pressure. In addition, the linear
solenoid 132a causes the line pressure regulator valve 132b to
maximize the line pressure PL at the time of current OFF, and to
decrease the line pressure PL when the current increases. The oil
drained from the line pressure regulator valve 132b is outputted,
as a first drain, to be supplied, as a converter pressure, to the
torque converter 3, and, as a second drain, to be returned to a
suction port of the oil pump O/P.
[0069] In FIG. 3, the hydraulic circuit is provided with a first
pressure switch 111, a second pressure switch 112, a third pressure
switch 113, a fourth pressure switch 114, a fifth pressure switch
115, a manual valve 116, a pilot pressure 117, a line pressure oil
passage 119, a pilot pressure oil passage 120, a D range pressure
oil passage 121, a R range pressure oil passage 122, a low clutch
pressure oil passage 124, a high clutch oil passage 125, a 2-6
brake pressure oil passage 126, a 3-5 reverse clutch pressure oil
passage 127, and a low & reverse brake pressure oil passage
128.
[0070] The first to the fifth pressure switches 111.about.115 are
established on the low clutch pressure oil passage 124, the high
clutch pressure oil passage 125, the 2-6 brake pressure oil passage
126, the 3-5 reverse clutch pressure oil passage 127, and the low
& reverse brake pressure oil passage 128, respectively, in
order to detect whether or not the engagement pressure is present
as a switch signal (ON when the engagement pressure is present, OFF
when the engagement pressure is absent).
[0071] In FIG. 3, the electronic shift control system is provided
with an A/T control unit 40, a vehicle speed sensor 41, a throttle
sensor 42, an engine speed (rpm.) sensor 43, a turbine speed (rpm.)
sensor 44, an inhibitor switch 45 that detects a lever operation by
the driver, and an oil temperature sensor 46.
[0072] The A/T control unit 40 inputs a switch signal from each of
the pressure switches 111.about.115 and a signal from each of the
sensors or switches 41.about.46, processes calculation based on
these pieces of input information and preset shift control rules
and failsafe rules, and outputs solenoid drive signals along with
the results of processed calculation to the first duty solenoid
106a, the second duty solenoid 107a, the third duty solenoid 108a,
the fourth duty solenoid 109a, the fifth duty solenoid 110a, and
the linear solenoid 132a. The detail of the A/T control unit 40
will be described later.
[0073] Based on FIGS. 4.about.8, there is description on the
structures of the pressure regulator valves 106b.about.110b, each
pressure regulating the engagement pressure, and also on the
structure of the line pressure regulator 132b.
[0074] FIGS. 4 and 5 are axial direction sections of the second
pressure regulator valve 107b. Basically, the second pressure
regulator valve 107b regulates the engagement pressure to a desired
oil (or hydraulic) pressure by regulating a ratio between an inflow
of oil from an original pressure port to an output port and an
outflow of oil from the output port to a drain port. Further, as
described below, the second pressure regulator valve 107b is set
such that the maximum of engagement pressure (discharged from the
output port) is equal to the maximum of line pressure PL (inputted
from the original pressure port).
[0075] In detail, settings are such that an x-axis is in an axial
direction of a valve spool and has a minus direction toward the
side where a spring is. From the side toward which the x-axis has a
plus direction, there are a solenoid pressure port, a drain port,
an output (high clutch pressure) port, an original pressure (D
range pressure=line pressure PL), and an output feedback pressure
port arranged in this order.
[0076] The second pressure regulator valve 107b controls the state
of communication between the original pressure port and the output
port and the state of communication between the output port and the
drain port in order to regulate the engagement pressure to a
desired oil pressure in an equilibrium state established when a
force, which is derived from a solenoid pressure delivered by the
second duty solenoid 107a as an operation signal pressure, to press
the spool in the minus direction of the x-axis balances with
forces, which are derived from the spring and from a feedback
pressure delivered via the high clutch oil passage, to press the
spool in the plus direction of the x-axis.
[0077] The solenoid pressure that is the operating signal pressure
becomes the highest when the second duty solenoid 107a is in the
state of solenoid OFF. When this operating signal pressure is
outputted, if the line pressure PL, is lower than the oil pressure
(the maximum of engagement pressure) which is determined by this
highest solenoid pressure, the spool is displaced to the maximum in
the minus direction of the x-axis to the position as indicated by
the lower half of the section shown in FIG. 4 to allow the original
pressure port to communicate with the output port and to open the
original pressure port to the maximum. Therefore, the output (high
clutch pressure) becomes the highest and as high the original
pressure (D range pressure=line pressure PL).
[0078] On the other hand, the solenoid pressure becomes the lowest
when the second duty solenoid 107a is in the state of solenoid ON.
Then, the spool is displaced to the maximum in the positive
direction of the x-axis to the position as indicated by the upper
half of the section shown in FIG. 5 to allow the output port to
communicate with the drain port and to open the drain port to the
maximum. In other words, the output (high clutch pressure) becomes
the lowest, that is, zero.
[0079] In addition, there is omitted description on the other
pressure regulator valves 106b, 108b.about.110b because they have
generally similar structures.
[0080] FIGS. 6.about.8 are axial direction sections of the line
pressure regulator valve 132b. Basically, the line pressure
regulator valve 132b regulates the ejection pressure of the oil
pimp O/P to a desired line pressure PL by regulating only a flow
from a line pressure port to drain ports (a first drain port and a
second drain port).
[0081] In detail, settings are such that an x-axis is in an axial
direction of the valve spool and has a minus direction toward the
side where a spring is. From the side toward which the x-axis has a
plus direction, there are a line pressure PL feedback port, a drain
port, a second drain port (drain toward the oil pump suction side),
a line pressure PL port, a first drain port (drain as a torque
converter pressure), an R range pressure port, which an R range
pressure acts on at the time of selection of the R range to change
the characteristics of the pressure regulator valve with respect to
the operating signal pressure, and a solenoid pressure port for a
solenoid pressure, as an operating signal pressure, for controlling
the line pressure arranged in this order.
[0082] The line pressure regulator valve 132b controls the state of
communication between the line pressure port and the first drain
port and the state of communication between the line pressure port
and the second drain port in an equilibrium state established when
forces, which are derived from the spring and from a solenoid
pressure delivered by the linear solenoid 132a, to press the spool
in the plus direction of the x-axis balance with a force, which is
derived from the oil pump ejection pressure feedback pressure, to
press the spool in the minus direction of the x-axis.
[0083] The solenoid pressure becomes the highest when the linear
solenoid 132a is in the state of current OFF. Then, for example, in
the range where the engine speed (rpm) is low and discharge of the
oil pump O/P is not sufficient, the spool is displaced to the
maximum in the plus direction of the x-axis to the position as
indicated by the section shown in FIG. 6, preventing the line
pressure port from communicating with the first drain port and the
second drain port neither. Therefore, the ejection pressure of the
oil pump O/P is supplied, unaltered, as the line pressure PL
because the oil ejected by the oil pump is not drained.
[0084] On the other hand, for example, in the range where the
engine speed (rpm) is high and sufficient discharge of the oil is
secured, when the solenoid pressure from the linear solenoid 132a
is the highest or lower than it, the spool is displaced in the
minus direction of the x-axis as indicated by the section shown in
FIG. 7 to allow the line pressure port to communicate with the
first drain port, draining a portion of the line pressure PL as the
torque converter pressure.
[0085] In addition, when the relation between the solenoid pressure
from the linear solenoid 132a and the ejection pressure of the oil
pump demands more than the first drain port can drain, the spool is
displaced further in the minus direction of the x-axis as indicated
by the section shown in FIG. 8, allowing the line pressure port to
communicate with the second drain port as well as the first drain
port.
[0086] Shift Control
[0087] Next, there is description on shift control. FIG. 9 is a
control block diagram showing the constitution of the A/T control
unit. As illustrated, connected to an input side of the A/T control
unit 4 are various sensors and/or switches 41.about.46,
111.about.115, while, connected to an output side of it are various
duty solenoids 106a.about.110a and linear solenoid 132a.
[0088] In addition, the A/T control unit 40 includes a target shift
stage determination section 401, a shift control section 402, an
inertia phase start detection section 403 and a shift at low
temperatures control section 404 and etc. These sections perform
calculations based on input information from the various sensors
41.about.46 and the pressure switches 111.about.115. These sections
also output solenoid drive signals to the duty solenoids
106a.about.110a and the linear solenoid 132a.
[0089] Among them, the target shift stage determination section 401
has a function to determine a target shift stage based on vehicle
driving information including an accelerator position and a vehicle
speed and it is memorized in the A/T control unit 40 as a shift
map.
[0090] The shift control section 402 starts shifting and carries
out shift control. In other words, it gives oil pressure order(s)
to the duty solenoids 106a.about.110a to engage the frictional
element(s) which accomplishes a new shift stage after a shift
(engagement side frictional element) and oil pressure order(s) to
disengage the frictional element(s) which accomplishes the current
shift state before the shift (disengagement side frictional
element). This shift control section 402 stores control programs
(control data) for all shift patterns beforehand, and, using these
memorized data, carries out shift control for a shift from the
current shift stage by .+-.1 stage.
[0091] In addition, the shift control section 402 gives an oil
pressure order to the linear solenoid 132a to pressure regulate the
line pressure PL. Setting of an order oil pressure is performed by
referring to line pressure maps memorized in the shift control
section 402.
[0092] FIG. 10 shows the line pressure maps. The line pressure maps
show the most suitable characteristics for input torque and they
are set to calculate high line pressure when input torque is big.
They make it possible to supply engagement pressure needed for each
of the frictional elements and calculate such a line pressure PL
that may reduce a loss of the oil pump O/P most.
[0093] There are several patterns for the line pressure maps, and
there are, as the line pressure maps which are referred to at
normal oil temperatures, line pressure maps during normal
non-shifting, which maps are referred to during normal
non-shifting, and line pressure maps during normal shifting, which
maps are referred to during shifting. As the line pressure maps
during normal non-shifting, there are a line pressure map at
forward range, which map is referred to at forward range, and a
line pressure map at reverse range, which map is referred to at
reverse range. As the line pressure maps during normal shifting,
there are a line pressure map during normal shifting at forward
range, which map is referred to during shifting at forward range
and a line pressure map during shifting at reverse range, which map
is referred to at reverse range.
[0094] In addition, there are a line pressure map at N-D select,
which map is referred to at a select from a non-drive range to a
forward drive range, and a line pressure map at N-R select, which
map is referred to at a select from the non-drive range to a
reverse drive range. In the first embodiment, the setting is such
that the line pressure map during shifting at forward range and the
line pressure map at N-D select give the same line pressure against
the same input torque, and the line pressure map during shifting at
reverse range and the line pressure map at N-k select give the same
line pressure against the same input torque. The line pressure maps
are not limited in particular so that the setting of these maps may
be tailored to performance requirements of different types of
vehicles, and the line pressure maps during shifting may be
referred to against input torque at select operation instead of
providing separate line pressure maps at select operation.
[0095] Furthermore, as line pressure maps that are referred to at
low temperatures when oil temperature is lower than a predetermined
value, there are a line pressure map during non-shifting at low
temperatures, which map is referred to during non-shifting at low
temperatures, and a line pressure map during shifting at low
temperatures, which map is referred to during shifting at low
temperatures. As line pressure maps during shifting at low
temperatures, there are a line pressure map during shifting at
forward range at low temperatures, which map is referred to at
forward range and a line pressure map during shifting at reverse
range at low temperatures, which map is referred at reverse
range.
[0096] In addition, there are a line pressure map at N-D select at
low temperatures, which map is referred to at a select from a
non-drive range to a forward drive range, and a line pressure map
at N-R select at low temperatures, which map is referred to at a
select from the non-drive range to a reverse drive range. In the
first embodiment, the setting is such that the line pressure map
during shifting at forward range at low temperatures and the line
pressure map at N-D select at low temperatures give the same line
pressure against the same input torque, and the line pressure map
during shifting at reverse range at low temperatures and the line
pressure map at N-R select at low temperatures give the same line
pressure against the same input torque. The line pressure maps are
not limited in particular so that the setting of these maps can be
tailored to performance requirements of different types of
vehicles, and the line pressure maps during shifting may be
referred to against input torque at select operation instead of
providing separate line pressure maps at select operation.
[0097] Furthermore, with the same input torque, the line pressure
map at non-shifting at low temperatures provides a higher oil
pressure than the line pressure map during shifting at low
temperatures (at forward range or reverse range) does. In addition,
the line pressure map during shifting at low temperatures (at
forward range or reverse range) provides a lower oil pressure than
the line pressure map during normal shifting (at forward range or
reverse range) does. In addition, the line pressure map at select
at low temperatures (at N-D or N-R) provides a lower oil pressure
than the line pressure map at normal select (at N-D or N-R)
does.
[0098] During non-shifting at normal temperatures, the shift
control section 402 gives an order to the linear solenoid 132a
based on input torque and the line pressure map at forward range
(or at reverse range) to control the line pressure regulator valve
132. This makes it possible to adjust the line pressure PL, which
is the ejection pressure of the oil pump O/P, to an appointed line
pressure value PL, thereby reducing a loss of the oil pump O/P
most.
[0099] During shifting, the shift control section 402 gives an
order to the linear solenoid 132a based on input torque during
shifting and the line pressure map during shifting at forward range
(or at reverse range) to control line pressure regulator valve 132.
This makes it possible to adjust the line pressure PL to an
appointed line pressure value PL, thereby improving shift feel.
[0100] The inertia phase start detection section 403 calculate an
actual gear ratio GR and a shifting progress degree SK based on
information from the turbine speed (rpm) sensor 44 and the like,
and detect or determine a start of inertia phase. In addition, this
inertia phase start detection section 403 can detect or determine
an end of inertia phase. Therefore, the inertia phase start
detection section 403 has a function of inertia phase end detection
section, too.
[0101] The shift at low temperatures control section 404 has a
shift judgment at-low-temperature section 405, an
engagement-pressure at-low-temperature regulation section 406, and
a line pressure at-low-temperature section 407. The shift judgment
at-low-temperature section 405 determines whether or not there is a
shift or a select from a non-drive range to a drive range at low
temperatures. The engagement-pressure at-low-temperature regulation
section 406 gives oil pressure orders to the duty solenoids
106a.about.110a to selectively engage an engagement side frictional
element and/or selectively disengage a disengagement side
frictional element during shifting at low or low temperatures. The
line pressure at-low-temperature section 407, which includes line
pressure maps for low temperatures (see FIG. 10) and gives an oil
pressure order to the linear solenoid 132a during shifting at low
temperatures or during non-shifting at low temperatures.
Operation of First Embodiment
[0102] Next, there is description on the first embodiment of a
control system.
[0103] There is description on concrete content of the shift
control. At normal time, namely, other than the case at low
temperatures, the shift control is carried out along the control
programs (control data) memorized beforehand in the shift control
section 402 to make an n.fwdarw.(n-1) shift if the shift is a
downshift or an n.fwdarw.(n+1) shift if the shift is an
upshift.
[0104] Normal Downshift Control
[0105] At first, referring to FIGS. 11 and 12, there is description
on a downshift at normal time other than at low temperatures
(normal downshift). FIG. 11 is a time chart of a normal downshift
control, and FIG. 12 is its flow chart.
[0106] The flow chart shown in FIG. 12 begins with step S1 to carry
out a downshift judgment. In other words, when, during a run with
the nth shift stage, driving conditions have changed to
predetermined conditions, the (n-1)th is set as a target shift
stage by a shift map, that is, the target shift stage determination
section 401, within the A/T control unit 40.
[0107] A normal downshift control from the nth shift stage to the
(n-1)th is started based on control signals from the shift control
section 402 when, in step S10, the temperature of automatic
transmission oil is equal to or higher than a predetermined value.
For example, the predetermined value can be set to -20.degree. C.,
where the automatic transmission oil has an extremely high
viscosity.
[0108] The normal downshift control comprises a normal engagement
pressure control and a normal line pressure control. With the
normal engagement pressure control, oil pressures on the engagement
and disengagement side (called in the following "engagement
pressures") are controlled by the shift control section 402 in
order to reduce engagement shock. With the normal line pressure
control, the line pressure PL is controlled by the shift control
section 402 in order to improve shift feel.
[0109] Normal Engagement Pressure Control
[0110] The following is description on normal engagement pressure
control, that is, the engagement pressure control during a normal
downshift.
[0111] Precharge Control: Engagement Side
[0112] With oil pressure control of an engagement side frictional
element, the precharge control (piston stand-by control) is carried
out (indicated at AC11 in FIGS. 11 and 12). This control is carried
out to let the piston complete a portion of its full stroke as soon
as possible and outputs an oil pressure order value to order oil
pressure high enough to let the piston stroke around 70% of its
full stroke. In addition, the oil pressure order value that is
outputted at this time results from adding a learning amount to a
preset value PA1 (PA1+learning amount).
[0113] And, immediately after outputting the above-mentioned oil
pressure order value (the preset value PA1+learning amount) for a
predetermined time T1, an oil pressure order value is decreased
once to set an oil pressure order value (a preset value
PA2+learning amount), which builds up oil pressure value high
enough to maintain the above-mentioned piston stand-by state, to
prepare for engagement. In addition, the learning is carried out
based on time and a rate of change until inertia phase.
[0114] Piston Stroke Control: Engagement Side
[0115] After elapse of the predetermined time T1, there is a shift
to a piston stroke control (as indicated at AC12 in FIG. 11). This
piston stroke control increases an oil pressure order value from
the above-mentioned oil pressure value (PA2+learning amount) at a
predetermined input torque dependent incline RA1 in order to
control a piston stroke of a clutch of the engagement side.
[0116] In this case, the setting is such that the predetermined
incline is the value which keeps oil pressure within a piston
chamber of the engagement side frictional element constant, and
this value of the predetermined incline is set by considering a
rise of actual oil pressure after the piston stroke control and
unevenness and the like of the piston stroke (step S103). In
addition, in the case of a power-on downshift, the later described
disengagement side frictional element lets the shift control make
progress, and in the case of a power-off downshift, the engagement
side frictional element lets the shift control make progress. On
this account, the predetermined incline RA1 in a power-on downshift
is gentler than that in a power-off downshift.
[0117] And the piston of the engagement side frictional element
strokes gradually under the constant pressure value which is
determined by such an oil pressure order value, and an oil pressure
switch is turned ON when the piston stroke is completed. On this
account, the piston stroke control comes to an end upon detecting
the oil pressure switch ON, and there is a shift to the next AC21
(step S104). In addition, a timer and the gear ratio GR are
monitored as the backing of the oil pressure switch so that, when
the oil pressure switch ON is not detected, the piston stroke
control is finished upon elapse of a predetermined time T2
beginning with the start of the piston stroke control or upon the
gear ratio GR achieving a predetermined gear ratio GR4 that is
higher than a gear ratio GR1 indicative of start of inertia
phase.
[0118] Undershoot Prevention Control: Disengagement Side
[0119] On the other hand, in a disengagement side frictional
element, at first, an undershoot prevention control is carried out
(RC11 in FIGS. 11 and 12). In other words, an oil pressure order
value is reduced to a predetermined oil pressure value TR2 that is
set depending on an input torque when the downshift is started.
Then, in order to prevent excessive drop of oil pressure
(undershoot), an oil pressure order value that is slightly higher,
by an amount (+TR1), than the oil pressure value which is to be
targeted is output at the start of the shift, and then the oil
pressure order value is gradually decreased to the above-mentioned
oil pressure value TR2 to be targeted by taking a predetermined
time T14 (steps S201, S202 of FIG. 12).
[0120] In addition, the oil pressure value TR2 mentioned above is
equivalent to oil pressure, with which inertia phase starts at the
time of a power-on downshift, of the degree that allows plates of
the disengagement side frictional element to begin to slip
slightly, In addition, it is equivalent to oil pressure of the
degree that does not allow clutch plates of the disengagement side
frictional element to slip at the time of a power-off
downshift.
[0121] Maintenance Control Prior to Clutch-to-Clutch Shift
Operation: Disengagement Side
[0122] And, there is a shift to a maintenance control prior to
clutch-to-clutch operation upon elapse of a predetermined time T14
(RC11 in FIGS. 11 and 12). This control maintains the current shift
stage by the disengagement side frictional element until completion
of the piston stroke of the disengagement side frictional element
by controlling the engagement pressure within the disengagement
side frictional element to the input torque dependent oil pressure
TR2 (step S203).
[0123] This is because neutral state is established to allow the
engine to race to cause an increase in engine rpm if, at the time
of a power-on downshift, the disengagement side frictional element
is disengaged when the engagement side frictional element is not
sufficiently prepared for engagement. In addition, at the time of a
power-off downshift, establishing neutral state allows the engine
rpm to drop toward an idle rpm, causing an increase in rotational
difference between the clutch plates of the engagement side
frictional element. In order to avoid such events, the maintenance
control prior to clutch-to-clutch shift operation is carried
out.
[0124] Afterwards, detection that the oil pressure switch is ON
(=the completion of piston stroke) or elapse of the time T2+T10
finish the maintenance control prior to clutch-to-clutch shift
operation (step S204).
[0125] By the way, when the above-mentioned AC11 and AC12 of the
engagement side frictional element and RC11 of the disengagement
side frictional element are finished, there is an advance to AC21
and RC21 next and a clutch-to-clutch shift operation is
started.
[0126] Clutch-to-Clutch Shift Operation Control: Disengagement
Side
[0127] In the disengagement side frictional element, upon
completion of the piston stroke (oil pressure switch ON or elapse
of T2+T10) at the time of a power-on downshift, the
clutch-to-clutch shift operation control decreases oil pressure at
the input torque dependent incline RP2 (step S205).
[0128] In addition, at the time of a power-off downshift, in many
cases, the inertia phase (RC31) is started before the
clutch-to-clutch shift operation is stared and there are many cases
that the clutch-to-clutch shift operation RC21 fails to take place,
but, if the inertia phase is started, this control is carried out
as the backing, hastening the start of the inertia phase by
decreasing oil pressure at the inline RR2.
[0129] And, when the gear ratio GR achieves the gear ratio GR1
indicative of start of inertia phase, there is a shift to an
inertia phase control by finishing the clutch-to-clutch shift
operation (step S206).
[0130] Clutch-to-Clutch Shift Operation Control: Engagement
Side
[0131] On the other hand, in the engagement side frictional
element, the clutch-to-clutch shift operation control increases the
oil pressure order value at a predetermined incline RA2 that is set
beforehand based on input torque and vehicle speed (step S105).
[0132] Here, the incline RA2 at the time of a power-off downshift
is set for every input torque and vehicle speed so that a pull
incline (a fall incline of output shaft torque) may become the most
suitable and it is set to become a big incline when an input torque
becomes big. In addition, the incline RA2 at the time of a power-on
downshift is set to become the lowest incline because the
engagement capacity is not needed if the piston stroke is
completed.
[0133] And, when the gear ratio GR achieves a predetermined gear
ratio GR5, there is a shift to an inertia phase control by
finishing the clutch-to-clutch shift operation of the engagement
side frictional element (step S106).
[0134] Inertia Phase Control: Disengagement Side
[0135] In the disengagement side frictional element, in the case of
a power-off downshift, when it starts, an inertia phase control
(AC31, RC31) decreases the oil pressure order value from an oil
pressure at the time of inertia phase detection at a predetermined
incline that is determined dependent on input torque and vehicle
speed.
[0136] In addition, in the case of a power-on downshift, it
controls shift progress with oil pressure within the disengagement
side frictional element by increasing the oil pressure order value
at an incline that is determined depending on input torque and
vehicle speed. It delays an output shaft torque fall and a progress
of the shift operation by keeping a clutch capacity in particular,
making it easy to synchronize the engagement side frictional
element in (n-1)th shift stage (step S207).
[0137] And, when the gear ratio GR reaches a gear ratio GR3 near a
gear ratio for the (n-1)th shift stage, the inertia phase control
is completed (step S208).
[0138] Inertia Phase Control: Engagement Side
[0139] In addition, in the engagement side frictional element, when
it starts, the inertia phase control increases the oil pressure at
a predetermined incline RA3 that is determined dependent on input
torque and vehicle speed.
[0140] In addition, at the time of a power-off downshift, the
incline RA3 is set to become gentle so that the progress of a shift
is gentle from the middle of the inertia phase to the end thereof
At the time of a power-on downshift, the incline RA3 is set to
become the lowest incline because the engagement capacity is not
needed (step S107).
[0141] And, when the gear ratio GR reaches a predetermined gear
ratio GR6 that is to be reached before the before-mentioned gear
ratio GR3, the inertia phase control is completed (step S108).
[0142] Inertia Phase End Control: Engagement Side
[0143] Afterwards, there is a shift to an inertia phase end control
(AC41) in the engagement side frictional element. This inertia
phase end control increases the oil pressure to a predetermined oil
pressure TA14 that is set beforehand based on an input torque
taking a predetermined time T12 (steps S109, S110). Here, the
predetermined oil pressure TA14 is high enough to securely fix the
(n-1)th shift stage and can prevent shift shocks occurring due to
unevenness upon detection of the end of inertia phase.
[0144] And, upon elapse of the predetermined time T12, the inertia
phase end control sets 100% as the oil pressure order value (duty),
outputting the maximum oil pressure (MAX pressure) to finish
shifting operation of the engagement side frictional element.
[0145] Diagonally Draining Chamfering Control: Disengagement
Side
[0146] On the other hand, in the disengagement side frictional
element, a diagonally draining chamfering control is carried out
when the inertia phase control comes to an end (RC41). The
diagonally draining chamfering control decreases the oil pressure
at a predetermined incline RR4 that is determined depending on an
input shaft upon judgment of the end of inertia phase, quickly
decreasing the oil pressure to the minimum oil pressure (zero oil
pressure) while suppressing torque variations of the output shaft
(step S209).
[0147] And, the diagonally draining chamfering control finishes
shifting in the disengagement side frictional element by setting 0%
as the oil pressure order value (duty) to order the minimum oil
pressure (MIN pressure=zero oil pressure) upon elapse of a
predetermined time T8 beginning with decreasing the oil pressure in
this way at the predetermined incline RR4.
[0148] As above, the normal engagement pressure control is carried
out by the shift control section 402.
[0149] Normal Line Pressure Control
[0150] In other words, in a normal downshift line pressure control,
a normal line pressure control reduces shift shocks by regulating
the line pressure PL that is the original pressure of the
engagement pressure supplied to the frictional element.
[0151] At the time of normal run free from shifting, the shift
control section 402 provides, as an output, an order to the linear
solenoid 132a based on line pressure map at forward range (see FIG.
10) to regulate the line pressure regulator valve 132. By this, the
line pressure is regulated to the line pressure PL.
[0152] As shown in the flow chart of FIG. 12, after the start of
the normal downshift, the shift control section 402 changes the
line pressure map for the line pressure map during shifting at
forward range (see FIG. 10) to control the line pressure regulator
valve 132b such that the line pressure PL becomes a predetermined
level of line pressure PL lower than the predetermined level of
line pressure before the start of the normal downshift (step
S701).
[0153] Both the line pressure map at forward range and the line
pressure map during shifting at forward range are set to calculate
predetermined levels of line pressure PL based on input torque.
Therefore, before and after the shift event, a change in levels of
line pressure PL is small. That is, when input torque is big, the
line pressure PL calculated other than shifting and the line
pressure PL calculated during shifting are both high. When input
torque is small, the line pressure PL calculated other than
shifting and the line pressure PL calculated during shifting are
both low. Therefore, in any one of the both cases, a change in
levels of line pressure PL is small before and after the shift
event.
[0154] Upon completion of clutch-to-clutch shift operation by
finishing engagement pressure control, the shift control section
402 changes the line pressure map for the original line pressure
map during non-shifting (line pressure map at forward range) (steps
S702 and S703).
[0155] As above, the shift control section 402 caries out the
normal downshift control.
[0156] Normal Upshift Control
[0157] Referring to FIGS. 13 and 14, there is description on an
upshift at normal time other than at low temperatures (normal
upshift). FIG. 13 is a time chart of a normal upshift control, and
FIG. 14 is its flow chart.
[0158] The flow chart shown in FIG. 14 begins with step S1 to carry
out an upshift judgment. In other words, when, during a run with
the (n-1)th shift stage, driving conditions have changed to
predetermined conditions, the nth is set as a target shift stage by
the target shift stage determination section 401 within the A/T
control unit 40.
[0159] A normal downshift control from the nth shift stage to the
(n-1)th is started based on control signals from the shift control
section 402 when, in step S10, the temperature of automatic
transmission oil is equal to or higher than a predetermined
value.
[0160] With the normal upshift control, the shift control section
402 carries out the normal line pressure control as well as the
normal engagement pressure control.
[0161] Normal Engagement Pressure Control
[0162] The following is description on normal engagement pressure
control, that is, the engagement pressure control during a normal
upshift.
[0163] Precharge Control and Piston Stroke Control: Engagement
Side
[0164] With oil pressure control of an engagement side frictional
element, a precharge control (piston stand-by control) is carried
out (AC11, steps S301, S302) at start of upshift operation, and a
piston stroke control is carried out (AC12, steps S303, S304).
Detailed description of these precharge control and piston stroke
control are hereby omitted because their control contents similar
to those mentioned in connection with the downshift.
[0165] Clutch-to-clutch Shift Operation Control: Engagement
Side
[0166] Next, a clutch-to-clutch shift operation control of AC21 is
started. This clutch-to-clutch shift operation control increases
oil pressure order value at a predetermined incline RA2 determined
based in input torque and vehicle speed (step S305), and there is a
shift to the next inertia phase control (step S306) after finishing
the clutch-to-clutch shift operation control when the gear ratio GR
becomes smaller than a predetermined gear ratio GR1.
[0167] Here, the predetermined incline RA2 is set so that a pull
incline (a fall incline of output shaft torque during a torque
phase) may become the most suitable and it is set to become a big
incline when an input torque becomes big. This oil pressure incline
RA2 is aimed also at preventing oil pressure surge and shift shocks
when clutch-to-clutch shift operation control is replaced by
inertia phase control. There is a case in which inertia phase is
detected before clutch-to-clutch shift operation is started and a
shift is made to the inertia phase without carrying out the present
control.
[0168] Inertia Phase Control: Engagement Side
[0169] When it is started, an inertia phase control (AC31)
increases the oil pressure at a predetermined incline that is
determined based on input torque and vehicle speed (step S307).
Here, the incline RA3 takes a value smaller than the incline RA2 of
the clutch-to-clutch shift operation control, allowing the oil
pressure to rise gently and comparatively slowly.
[0170] And, when the gear ratio GR reaches an inertia phase end
gear ratio GR2, the inertia phase control is completed (step
S308).
[0171] Inertia Phase End Control: Engagement Side
[0172] Next, there is a shift to an inertia phase end control
(AC41). This inertia phase end control increases the oil pressure
at an incline RA4 (constant) larger than the predetermined incline
RA3 taking a predetermined time T8. In addition, the oil pressure
is allowed to rise at the predetermined incline RA4 because shift
shocks caused by unevenness upon detection of the end of inertia
phase may occur if the oil pressure order value is increased at a
stretch (steps S309, S310).
[0173] And, upon elapse of the predetermined time T8, the inertia
phase end control sets 100% as the oil pressure order value (duty),
outputting the maximum oil pressure (MAX pressure) to finish the
engagement pressure control of the engagement side frictional
element.
[0174] Undershoot Prevention Control and Maintenance Control prior
to Clutch-to-Clutch Shift Operation: Disengagement Side
[0175] On the other hand, in a disengagement side frictional
element, at first, an undershoot prevention control is carried out
(steps S401, S402). Later, there is a shift to a maintenance
control prior to clutch-to-clutch shift operation. In other words,
as shown in FIG. 13, an oil pressure order value is reduced to a
predetermined order value TR2 when an upshift is started.
[0176] Then, in order to prevent excessive drop of oil pressure
(undershoot), the target oil pressure order value is gradually
decreased to the above-mentioned oil pressure order value TR2 to be
targeted by taking a predetermined time T15. In addition, the
above-mentioned oil pressure order value TR2 is the limit value
that a clutch of the disengagement side frictional element does not
slip.
[0177] And, with the oil pressure maintained in such a limit value
TR2 by the maintenance control prior to clutch-to-clutch shift
operation (RC11), the torque capacity of the clutch drops and
shifting starts progressing immediately after a drop in oil
pressure when there is a shift to the clutch-to-clutch shift
operation. In addition, at the time of a power-off upshift, a
constant oil pressure order value TR3 (<TR2) is applied instead
of the above-mentioned oil pressure order value TR2.
[0178] Clutch-to-clutch Shift Operation Control: Disengagement
Side
[0179] Next, a clutch-to-clutch shift operation control (RC21) is
started. This clutch-to-clutch shift operation control sets an
incline of oil pressure order value such that the oil pressure
order value may become an oil pressure order value TR3 at the time
of the above-mentioned power-off upshift upon elapse of a
predetermined time T16, and decreases the oil pressure order value
gradually at this incline.
[0180] And, the oil pressure order value reaches the oil pressure
order value TR3 upon elapse of the predetermined time T16, and
there is a shift to a drain control at inertia phase RC31 after the
oil pressure order value keeps the value TR3 until the gear ratio
GR reaches an inertia the gear ratio GR1. In addition, there is a
shift to a drain control at inertia phase (step S406) in time when
the gear ratio reaches the inertia phase start gear ratio GR1
before elapse of the predetermined time T16.
[0181] Drain Control at Inertia Phase: Disengagement Side
[0182] When it is started alter a shift, the drain control at
inertia phase control gradually decreases the oil pressure order
value at a gentle incline such that it may take a predetermined
time T17 for the oil pressure order value to become an oil pressure
of 0 (step S407). Here, the reason why this control does not
decrease the oil pressure order value to 0 (zero) at a stretch is
to avoid outbreak of shocks. In other words, setting a time needed
for gear ratio to reach a shifting end gear ratio from an inertia
phase start gear ratio GR1 as the predetermined time T17, the
control completes shifting operation without shift shocks by
gradually decreasing the oil pressure during this predetermined
time T17.
[0183] And, while decreasing, in this way, the oil pressure, upon
elapse of a predetermined time T8 after judgment that the gear
ratio reaches a gear ratio GR2, this control completes the shifting
operation by setting 0 as the oil pressure order value (step
S408).
[0184] Normal Line Pressure Control
[0185] Line pressure control at a normal upshift is similar to that
at a normal downshift. As above, the normal upshift control is
carried out by the shift control section 402.
[0186] Normal Select Control
[0187] Referring to FIGS. 15 and 16, there is description on a
select control at normal time other than at low temperatures
(normal select control). FIG. 15 is a time chart of a normal select
control, and FIG. 16 is its flow chart.
[0188] Select Control
[0189] The flow chart shown in FIG. 16 begins with step S1 to carry
out a select judgment. In other words, when the driver, which is
out of the frame, operates a lever to select ranges from N range
position to run range (D range or R range) position during
operation of the engine, the inhibitor switch 45 detects the
selected range position (corresponding to a lever operation
detection section). Depending on a kind of the selected range, the
shift control section decides which of the frictional elements
should be hydraulically controlled as follows:
[0190] As shown in FIG. 2, select operation from N range position
to D range position is normally achieved by engaging the low clutch
LOW/C and the low one-way clutch LOW/OWC. The shift control section
402 controls only the low clutch LOW/C because the low one-way
clutch LOW/OWC automatically engages. Although the present
invention is not limited to the following in particular, in
addition, when installed with select control logic that engage a
frictional element via a high shift stage, a frictional element to
be engaged according to this logic should be appropriately
selected.
[0191] Select operation from N range position to engine braking
range position (D1 range or M1 range) is achieved by engaging the
low clutch LOW/C and the low & reverse brake L&R/B. The
shift control section 402 controls both the low clutch LOW/C and
the low & reverse brake L&R/B.
[0192] Select operation from N range position to R range position
is achieved by engaging the 3-5 reverse clutch 3-5R/C and the low
& reverse brake L&R/B. The shift control section 402
controls both the 3-5 reverse clutch 3-5R/C and the low &
reverse brake L&R/B.
[0193] A normal select control is started when, in step S10, the
temperature of automatic transmission oil is equal to or higher
than a predetermined value after the select judgment (step S3). The
normal select control comprises a normal engagement pressure
control and a normal line pressure control.
[0194] Normal Engagement Pressure Control
[0195] The engagement pressure control, at the time of select
operation, carries out control of supply oil pressure to a
frictional element A1 and/or a frictional element A2. Here, the
frictional elements A1 and A2 are engagement side frictional
elements (corresponding to a first frictional element). As
described later, the oil pressure control for the frictional
element A1 (A1 engagement control) carries out inertia phase
control to reduce shift shocks, while, the oil pressure control for
the frictional element A2 (A2 engagement control) does not carry
out inertia phase control, but carries out control causing the
engagement pressure to rise quicker than the first frictional
element A1. Because a change in revolution of a rotary member
within the automatic transmission occurs due to rise in oil
pressure established in each of the frictional elements A1 and A2
and the energy due to an inertia change derived from the change in
revolution is added as an output shaft torque, it is decided to
call an engagement transient state (when progress of shift SK,
which is described later, is changing from 0% to 100%) at the time
of select operation, in particular, an inertia phase in this
embodiment.
[0196] The engagement pressure control at the time of select
operation determines the timings of start of inertia phase, end
thereof and each of control phases in response to the progress of
shift SK. The progress of shift SK is an index value based on the
quantity of slip within a torque converter and calculated as,
SK=[Ne-(current Nt)]/[Ne-(Nt at end of select)]. The progress of
shift SK shows progress degree of shifting (select), and it is 0%
when current Nt is equal to Ne, and it is 100% at the time of
select end. Here, Nt shows transmission input speed (rpm) and Ne
shows engine speed (rpm).
[0197] When the progress of shift SK is greater than or equal to a
predetermined value SKO at the time of select judgment, the
shifting progresses under control in open mode by maximizing oil
pressure order values for the frictional element A1 and/or
frictional element A2 without any control afterwards. The following
is description on the case in which the progress of shift SK at the
time of select judgment is less than the predetermined value
SK0.
[0198] First, there is description on A1 engagement control, which
is oil pressure control of the frictional element A1 side.
[0199] Precharge Control and Piston Stroke Control
[0200] In the same manner as the engagement pressure control at
normal downshift (upshift), a precharge control (stand-by control)
is carried out at start of select (AC1, steps S501, S502), and then
a piston stroke control is carried out (AC2, steps S503, S504).
[0201] The piston stroke control (AC2) determines that a piston
stroke of the frictional element A1 is completed upon detection of
oil pressure switch ON. Therefore, the piston stroke control (AC2)
comes to an end, and there is a shift to the next inertia phase
control (AC3) (step S504).
[0202] In addition, a timer and the progress of shift SK are
monitored as the backing of the oil pressure switch so that, when
the oil pressure switch ON is not detected, the piston stroke
control (AC2) is finished and the inertia phase control (AC3) is
started (step S504) upon elapse of a predetermined time T2
beginning with the start of the piston stroke control (AC2) or when
the progress of shift SK increases by a predetermined value.
[0203] Based on FIG. 17, there is concrete description on judgment
processing to determine start of the inertia phase control (AC3)
based on increasing of the degree of shift SK. Judgment on start of
AC3 is permitted upon elapse of a predetermined time T3 (<T2)
beginning with start of AC2. In this judgment processing, one job
calculates .DELTA.SK=(SK by this time job)-(SK by last time job),
and this job is repeated multiple times in succession. It is
determined that AC3 is to be started when the job that calculated
.DELTA.SK bigger than or equal to a predetermined value SK1
occurred a predetermined N times in succession.
[0204] Inertia Phase Control
[0205] The inertia phase control (AC3) increases an oil pressure
order value at a predetermined incline RA2 that is set beforehand
based on input torque and vehicle speed (step S505). Here, the
predetermined incline RA2 is set so that an incline of the output
torque during the inertia phase may become the most suitable and it
is set to become a big incline when an input torque becomes
big.
[0206] When the progress of shift SK becomes greater than a
predetermined value SK5, an inertia phase second half control (AC4)
is started by finishing the inertia phase control (AC3) (step
S506).
[0207] Inertia Phase Second Half Control
[0208] When it is started, the inertia phase second half control
(AC4) increases the oil pressure at a predetermined incline RA3
that is set based on input torque and vehicle speed (step S507).
Here, the incline RA3 takes a value smaller than the incline RA2,
allowing the oil pressure to rise at a gentle incline and
comparatively slowly. And, AC4 is finished upon elapse of a
predetermined time T6 (step S508).
[0209] Inertia Phase End Control
[0210] Next, there is a shift to an inertia phase end control
(AC5). This inertia phase end control increases the oil pressure at
an incline RA4 (constant) larger than the predetermined incline.
RA3 taking a predetermined time T7 (steps S509, S510). The oil
pressure is allowed to rise at the predetermined incline RA4
because shift shocks caused by unevenness upon detection of the end
of inertia phase may occur if the oil pressure order value is
increased at a stretch.
[0211] And, upon elapse of the predetermined time T7, the inertia
phase end control sets 100% as the oil pressure order value (duty),
outputting the maximum oil pressure (MAX pressure) to finish the
engagement control of the frictional element A1 (steps S510,
S511).
[0212] A2 Engagement Control
[0213] Next, there is description on A2 engagement control, which
is oil pressure control of the frictional element A2 side.
[0214] Precharge Control and Piston Stroke Control
[0215] In the same manner as the A1 engagement control, a precharge
control (stand-by control) is carried out at start of select
(AC1(2), steps S601, S602), and then a piston stroke control is
carried out (AC2(2), step S603). The piston stroke control AC2(2)
increases the oil pressure order value at a predetermined incline,
and there is a shift to AC3(2) upon elapse of a predetermined time
T2(2) (step S604).
[0216] Oil Pressure Rise Control
[0217] Oil pressure rise control (AC3(2)) increases the oil
pressure order value at a predetermined incline RA2(2) (step S605).
Here, the incline RA2(2) takes a larger value than the incline
RA2(1) of AC2(2) so that the oil pressure may be increased quickly
at a steep incline. The control AC3(2) is finished upon elapse of a
predetermined time T3(2).
[0218] And, 100% is set as the oil pressure order value (duty),
outputting the maximum oil pressure (MAX pressure) (AC4(2), step
S607) to finish the engagement control of the frictional element
A2.
[0219] Normal Line Pressure Control
[0220] Line pressure control at normal select is the same as line
pressure at normal downshift (upshift). In addition, in N range,
line pressure is determined based on the line pressure map during
normal non-shifting (line pressure map at forward range), and, at a
select from N range to D range (engine braking range), the line
pressure map at N-D select as shown in FIG. 10 is used (step S801).
On the other hand, at a select from N range to R range, the line
pressure map at N-R select as shown in FIG. 10 is used (step S801).
After completion of engagement, the line pressure map is changed
for the line pressure map during normal non-shifting (line pressure
map at forward range or line pressure map at reverse range).
[0221] Shift Control at Low Temperatures
[0222] In order to prevent shift shocks, the shift at low
temperatures control section 404 carries out shift control at low
temperatures during a shift, which is meant to include a select,
and so on, at low temperatures, in which the fluidity of automatic
transmission oil drops.
[0223] The shift control at low temperatures comprises an
engagement control at low temperatures and a line pressure control
at low temperatures. In the engagement pressure control at low
temperatures, the engagement pressure at-low-temperature regulation
section 406 regulates supply oil pressure to the frictional
elements, while, in the line pressure at low temperatures, the line
pressure at-low-temperature regulation section 407 regulates line
pressure PL.
[0224] Downshift Control at Low Temperatures
[0225] Referring to FIGS. 18 and 19, there is description on a
downshift at low temperatures. FIG. 18 is a flow chart of the
downshift at low temperatures, and FIG. 19 is its time chart.
[0226] The flow chart shown in FIG. 18 begins with step S1 in which
the target shift stage determination section 401 carries out a
downshift judgment based on vehicle speed and throttle opening
degree. In step S10, the shift judgment at-low-temperature section
405 determines that the downshift is a downshift at low
temperatures when oil temperature detected by the oil temperature
sensor 46 is lower than a predetermined value. With the judgment of
the downshift at low temperatures, a downshift control at low
temperatures, which includes an engagement pressure control at low
temperatures and a line pressure control at low temperatures, is
performed.
[0227] Engagement Pressure Control at Low Temperatures
[0228] In the engagement pressure control at low temperatures, the
engagement pressure at-low-temperature regulation section 406
outputs an oil pressure order to one of the oil pressure regulator
valves 106.about.110 for the frictional elements to regulate
engagement pressure to the frictional element.
[0229] Engagement Side Engagement Pressure Control
[0230] An engagement pressure control for an engagement side
frictional element starts counting of a timer concurrently with the
downshift judgment, and, maximizes the oil pressure order for one
of duty solenoids 106a.about.110a upon elapse of a predetermined
timer T1 (steps S11, S12). In addition, in the first embodiment, a
downshift start occurs at a moment when a shift judgment occurs and
it is this moment when a disengagement side engagement pressure
control to be described later minimizes an oil pressure order.
[0231] The engagement pressure on the engagement side needs to rise
to an oil pressure high enough to finish an inertia phase by the
end of the inertia phase. Therefore, putting an output timing of an
oil pressure order for the engagement side on hold for the
predetermined time T1 beginning with a downshift start prevents
outbreak of interlock due to a delay in draining oil pressure on
the disengagement side. Therefore, the predetermined timer T1 is
set based on oil temperature (corresponding to a second
period).
[0232] The term "interlock" is herein used refers to a state in
which all of the rotary members are forced in directions decreasing
their revolutions toward zero because both a frictional element to
be engaged and a frictional element to be disengaged possess torque
capacity. Outbreak of such an interlock at downshift increases
depth of an output torque drop (pull feel), causing shift shocks to
occur. The outbreak of such shift shocks is prevented by providing
the predetermined timer T1.
[0233] Disengagement Side Engagement Pressure Control
[0234] On the other hand, the engagement pressure control for a
disengagement side frictional element minimizes an oil pressure
order for engagement to another of the duty solenoids
106a.about.110a immediately after the downshift judgment (step
S22). This prevents a drain delay in oil pressure on the
disengagement side. Afterwards, the minimized oil pressure order
for engagement is maintained.
[0235] As mentioned above, in order to prevent interlock due to a
drain delay in oil pressure on the disengagement side, the output
timing of an oil pressure order on the engagement side is delayed
by installing the predetermined timer T1 in the control on the
engagement side. However, the output timing of an oil pressure
order on the disengagement side is delayed by installing the
control on the disengagement side with varying predetermined timers
with different shifts because there is the case that a drain in oil
pressure on the disengagement side may become earlier depending on
different combinations of frictional elements selected as objects
to be controlled (step S21). The above-mentioned predetermined
timers are set depending oil temperature. In addition, in this
case, 0 (zero) is set as the predetermined timer T1 in the control
on the engagement side.
[0236] It is determined that an inertia phase is ended (step S23)
when the gear ratio GR becomes greater than a gear ratio GR3 after
minimizing the oil pressure order on the disengagement side (step
S22). This ends the engagement side engagement pressure control. In
addition, a backing timer T2 is monitored as the backing of the
inertia phase end judgment by gear ratio so that, when the gear
ratio does not meet the relationship GR>GR3, the engagement
pressure control is finished upon elapse of the predetermined time
T2 beginning with the downshift start (step S24).
[0237] Line Pressure at Low Temperatures
[0238] Keeping the engagement order for the engagement side
frictional element maximized until the end of shift is found to be
effective in getting rid of a drop in response in engagement
pressure of the engagement side frictional element at low
temperatures, uneven time until start of engagement and oil
pressure variations, but it leaves the regulator valves
106b.about.110b fully open. In this case, high line pressure is
abruptly supplied, as a supply pressure, to the engagement side
frictional element and giving fear that shift shocks grow big. This
explains why there is a need for performing the following line
pressure control at low temperatures.
[0239] In the line pressure control at low temperatures, at the
time of run free from shifting at low temperatures, the shift
at-low-temperature control section 404 provides, as an output, an
order to the linear solenoid 132a based on input torque and line
pressure map during non-shifting at low temperatures (see FIG. 10)
to regulate the line pressure regulator valve 132. By this, the
line pressure is regulated to a predetermined line pressure PL
(line pressure during non-shifting at low temperatures).
[0240] When it determines that there is a downshift at low
temperatures, the shift at low temperatures control section 404
changes the line pressure map during non-shifting at low
temperatures for the line pressure map during shifting at forward
range at low temperatures (see FIG. 10) to start line pressure
control thereby to start shifting (step S71). With the same input
torque, the line pressure map during shifting at forward range at
low temperatures is set lower than the line pressure map during
non-shifting at low temperatures and the line pressure maps during
normal non-shifting. It is necessary to always maintain the pilot
pressure, which is the original pressure of solenoids, in a stable
state by setting the line pressure rather high at the time of
shifting at normal oil temperatures in which hydraulic precision is
required because the duty solenoids 106a.about.110a and linear
solenoid 132a, which control pressure regulator valves, are heavily
dependent on the original pressure (the outputted solenoid
pressures fluctuate depending on changes of the pilot pressure that
is the original pressure). On the other hand, it is not necessary
to let the duty solenoids 106a.about.110a control the pressure
regulator valves with good precision, so that, with the same input
torque, the line pressure at low temperatures is set lower than the
line pressure map during normal shifting.
[0241] It is preferable that the predetermined line pressure that
is calculated from the line pressure map during shifting at low
temperatures (line pressure at low temperatures) is equal to the
lower limit of the engagement side engagement pressure needed to
finish an inertia phase, but it is set slightly higher than the
above-mentioned lower limit. This setting results from considering
low response characteristics of line pressure at low temperature
and difficulty to regulate oil pressure closely in accordance with
an order, and the line pressure at low temperatures is set at an
oil pressure that is given by multiplying the lower limit value of
the engagement side engagement pressure needed to finish the
inertia phase with a safety factor (=1.2 for example).
[0242] In addition, response characteristic of line pressure drops
in the same manner as the engagement pressure, but it is guaranteed
that the line pressure PL drops to the above-mentioned set oil
pressure before the engagement side engagement pressure rises to a
pressure level in the neighborhood of the line pressure PL because
the line pressure PL is regulated immediately after the downshift
start (step S71).
[0243] The line pressure control is ended by changing the line
pressure map during shifting at low temperatures for the line
pressure map during non-shifting at low temperatures (line pressure
map during non-shifting at forward range at low temperatures) when
the engagement pressure control at low temperatures for the
frictional element is ended (steps S72, S74). In addition, a
backing timer T3 is monitored as the backing of the line pressure
control end judgment based on the engagement pressure control end
judgment so that the line pressure control is ended upon elapse of
a predetermined time T3 beginning with the downshift start (steps
S73, S74).
[0244] As shown in FIG. 19, at time t1, simultaneously with a
downshift judgment at low temperatures, an oil pressure order for a
disengagement side frictional element is minimized (an order for
complete disengagement), and a shift is started. Because the
disengagement order for the disengagement side is outputted
simultaneously with the shift start, a delay in draining oil
pressure from the disengagement side frictional element is
prevented, facilitating progress of shift at low temperatures.
[0245] In addition, at time t1, the line pressure PL is decreased
to the oil pressure which is set high enough to end an inertia
phase. Afterwards, this oil pressure is maintained until the end of
downshift at low temperatures.
[0246] At t2 upon elapse of a predetermined time from t1 when the
downshift starts, actual oil pressure (called hereinafter
"engagement pressure") on the disengagement side starts actually
dropping.
[0247] At t3 upon elapse of a predetermined timer T1 beginning with
t1 when the downshift starts, an oil pressure order for an
engagement side frictional element is maximized (an order for
complete engagement). Afterwards, the maximized oil pressure order
continues. At t4 upon elapse of a predetermined time from t3,
engagement pressure on the engagement side starts rising
actually.
[0248] When the maximized oil pressure order is issued at t3, the
opening degree of an original port of the pressure regulator valve
106b.about.110b is the largest. This is because the oil pressure
high enough to end the inertia phase is lower than the maximum of
engagement pressure of the pressure regulator valve
106b.about.110b, and the opening degree of the original pressure
port is the largest regardless of the relation between the maximum
of the engagement pressure of the pressure regulator valve
106b.about.110b and the maximum of the line pressure PL. On this
account, the drop of response characteristic of the engagement
pressure on the engagement side is decreased even if the fluidity
of working fluid drops at low temperatures. That is to say, the
time from the oil pressure order t3 to the oil pressure rise t4 is
sufficiently short so that the outbreak of shift shocks due to
delay in response of engagement side engagement pressure may be
avoided.
[0249] The unevenness of time from the oil pressure order t3 to the
oil pressure rise t4 is reduced because the maximum oil pressure is
ordered in succession at t3 and afterwards.
[0250] At t3 upon a delay of a predetermined period T1 that is
based on oil temperature from t1, an oil pressure order for the
engagement side is issued. On this account, the outbreak of
interlock is prevented because the situation in which the
disengagement side frictional element still have torque capacity
when the torque capacity of the engagement side frictional element
is growing will not happen even if time from t1 to t2 becomes long
due to response delay of the disengagement side engagement
pressure.
[0251] At t5 upon elapse of a predetermined time from engagement
side engagement pressure rise t4, the disengagement side frictional
element starts slipping, and gear ratio GR starts increasing. In
other words, inertia phase starts at t5.
[0252] At t6 upon elapse of a predetermined time from t2 when the
disengagement side engagement pressure starts dropping, the
disengagement side engagement pressure becomes zero, completing
disengagement of the disengagement side frictional element. In
addition, at t6, the engagement side engagement pressure rises to
the neighborhood of the line pressure PL. Because the original
pressure port of the pressure regulator valve 106b.about.110b of
the engagement side frictional element is opened to the largest
opening degree, the ceiling of the engagement side engagement
pressure is the line pressure PL that is the original pressure.
[0253] At t7, the engagement side engagement pressure becomes as
high as the line pressure PL. On the other hand, the line pressure
PL is reduced to the line pressure during shifting at low
temperatures from t1 in succession. Therefore, the ceiling of the
engagement side engagement pressure is the line pressure during
shifting at low temperatures. Here, the line pressure during
shifting at low temperatures is set as high as an oil pressure that
is high enough to end the inertia phase so that the engagement side
engagement pressure may rise high enough to end the inertia
phase.
[0254] There is a reduction in speed at which torque capacity of
the engagement side frictional element increases owing to the
lowered ceiling of the engagement side engagement pressure, causing
a reduction in rise in engine rpm. Therefore, the outbreak of shift
shocks (excessive engine braking feel due to a reduction in output
torque) is prevented because the quantity of a reduction in output
torque per a unit time becomes small.
[0255] At t8, the gear ratio GR becomes equal to a gear ratio GR3
after the downshift, ending the inertia phase. By this, the
engagement pressure control is ended, and the line pressure during
shifting at low temperatures is changed for the normal line
pressure to calculate the line pressure PL. The engagement side
engagement pressure starts rising because the ceiling of the
engagement side engagement pressure rises with a rise of line
pressure PL.
[0256] At t9 upon elapse of a predetermined time from t8, the
engagement side engagement pressure rises to the neighborhood of
the normal line pressure to secure engagement of the engagement
side frictional element.
[0257] Oil Pressure Vibrations of Pressure Regulator Valve for
Frictional Element
[0258] The pressure regulator valves 106b.about.110b are subject to
great changes in movement of a valve spool within a very short
period of time or oil pressure vibrations during controlling the
pressure regulation of engagement pressure to the frictional
element at low temperatures in the same way as at normal
temperatures to materialize a supply of precharge pressure (high
pressure state) from oil pressure zero (low pressure state), a
supply of maintenance oil pressure (low pressure state), and a
supply of oil pressure for progress of inertia phase. And, in an
low temperature state when the response characteristic of oil
pressure drops, there is apprehension that such oil pressure
vibrations might be out of control once they occur.
[0259] As shown in FIGS. 4 and 5, the pressure regulator valve
106b.about.110b for engagement pressure controls a ratio between an
inflow of oil and an outflow of oil via two kinds of states, viz.,
a communication state between a drain port and an output port and a
communication state between an original pressure port and the
output port, without allowing any concurrent communication between
the drain port and the original pressure port. In other words, the
engagement pressure which is dependent on a solenoid pressure is
regulated when a valve spool stays in an equilibrium position at
which the inflow of oil to and the outflow of oil from the pressure
regulator valve 106b.about.110b are balanced with each other.
[0260] Therefore, controlling pressure regulation by subjecting the
valve spool to great changes in movement within a very short period
of time, as mentioned before, will cause oil vibrations to occur.
And, the outbreak of such oil vibrations cannot be controlled at
low temperatures when the response characteristic of oil pressure
drops because, in the pressure regulator valve 106b.about.110b of
the type which regulates engagement pressure by controlling a ratio
between the inflow to the valve and the outflow from the valve, it
is hardly possible to control the quantity of the above-mentioned
two flows once such oil vibrations occur.
[0261] Therefore, as mentioned above, the first embodiment
maximizes the opening degree of an original pressure port of the
pressure regulator valve 106b.about.110b for the engagement side
frictional element by performing a maximum pressure order for the
pressure regulator valve 106b.about.110b. In addition, the opening
degree of the original pressure port continues to be the largest
because the maximum pressure order for the pressure regulator valve
106b.about.110b in succession for a constant period of time.
Therefore, the oil pressure vibrations will not occur because the
pressure regulator valve 106b.about.110b is kept out of operation
for the constant period of time. As a result, the situation that
oil pressure vibrations occur and become uncontrollable at low
temperatures is prevented.
[0262] Oil Pressure Vibrations of Line Pressure Regulator Valve
[0263] In addition, for the following reasons, outbreak of oil
pressure vibrations by the line pressure regulator valve 132b is
prevented, too. As shown in FIGS. 6.about.8, the line pressure
regulator valve 132b has the structure that the drain port (the
first drain port, the second drain port) and the original pressure
port (the line pressure port) are simultaneously communicable with
each other, and determines the amount of pressure reduction in the
original pressure by the degree of opening, i.e., the amount of
drain. It regulates the line pressure PL by carrying out
proportional control of the linear solenoid to control the amount
of movement of the valve spool thereby to control only the amount
of an outflow from the valve (one quantity of oil). In other words,
in the range where the oil pump discharge is enough, the line
pressure regulator valve 132b is in a state shown in FIG. 7 by
always draining oil basically, and always, so to speak, in a
pressure equilibrium state.
[0264] Therefore, the line pressure regulator valve 132b does not
need to control anything but one quantity as compared to the
pressure regulator valves 106b.about.110b for frictional elements
when an order is issued for the valve to lower the pressure to a
lower limit pressure capable of finishing an inertia phase during
shifting because it is of the type capable of adjusting the
pressure by controlling only the quantity of outflow from the line
pressure port to the drain port. Besides, as mentioned above, the
line pressure regulator valve 132b is always in a pressure
equilibrium state. Because of this, there is no apprehension that
oil pressure vibrations may occur by the line pressure regulator
valve 132b.
[0265] Furthermore, the oil pressure vibrations are prevented from
occurring because a constant oil pressure order for the line
pressure regulator valve 132b is issued for a predetermined period
in succession during shifting and the period for which the constant
oil pressure order is issued is long.
[0266] Upshift Control at Low Temperatures
[0267] Referring to FIGS. 20 and 21, there is description on an
upshift control at low temperatures. FIG. 20 is a flow chart of the
downshift at low temperatures, and FIG. 21 is its time chart.
[0268] As shown in FIG. 20, the target shift stage determination
section 401 carries out an upshift judgment (step S1). The shift
judgment at-low-temperature section 405 determines that the upshift
is an upshift at low temperatures when oil temperature detected by
the oil temperature sensor 46 is lower than a predetermined value
(step S10). With the judgment of the upshift at low temperatures,
in the same manner as the downshift control at low temperatures, an
upshift control at low temperatures, which includes an engagement
pressure control at low temperatures and a line pressure control at
low temperatures, is performed.
[0269] Engagement Pressure Control at Low Temperatures
[0270] With the engagement pressure control on the engagement side,
immediately after start of the shift, an oil pressure order for
engagement is maximized (step S31). This shortens an oil pressure
rise time on the engagement side. Afterwards, the maximized oil
pressure order continues to be issued in succession. By this, oil
pressure vibrations will not occur in the pressure regulator valve
106b.about.110b, leading to prevention of the situation that such
oil pressure vibrations become out of control. In addition, in the
first embodiment, an upshift start is the moment upon making an
upshift judgment as well as the moment upon maximizing an oil
pressure order in the engagement pressure control on the engagement
side at low temperatures carried out simultaneously with this
judgment.
[0271] Engagement side engagement pressure control is ended when it
is determined that the gear ratio GR becomes equal to or smaller
than GR2 (step S32) after the output of an engagement order. In
addition, a backing timer T2 is monitored as the backing of the
inertia phase end judgment by gear ratio so that, when the gear
ratio does not meet the relationship GR.ltoreq.GR2, the inertia
phase is ended upon elapse of the predetermined time T2 beginning
with the downshift start (step S33).
[0272] With the engagement pressure control on the disengagement
side, upon elapse of a predetermined timer T1, which is different
from the predetermined timer T1 used in the downshift control at
low temperatures, and so on, (corresponding to a first period, an
oil pressure order is minimized, and the control is ended with the
minimized oil pressure order kept in succession (steps S41, S42).
Actual oil pressure rise of the engagement side is waited for by
putting an output timing of a disengagement order for the
predetermined timer T1. This prevents engine race due to a delay in
response characteristic of the engagement side engagement pressure.
Therefore, the predetermined timer T1 is set based on oil
temperature.
[0273] Line pressure control in the upshift control at low
temperatures is the same as the line pressure control in the
downshift control at low temperatures.
[0274] As shown in FIG. 21, at time t1, simultaneously with an
upshift judgment at low temperatures, an oil pressure order for an
engagement side frictional element is maximized. Because the
engagement order for the engagement side is outputted
simultaneously with the shift start, a delay in oil pressure rise
on the engagement side is prevented, facilitating progress of shift
at low temperatures.
[0275] In addition, at time t1 (at an upshift start), the line
pressure PL is decreased to the oil pressure during shifting at low
temperatures, and, afterwards, this oil pressure is maintained
until the end of upshift at low temperatures.
[0276] At t1 when the upshift starts, the oil pressure order for
the disengagement side is maximized and the engagement pressure on
the disengagement side is equal to the line pressure PL. As a
result from lowering the line pressure PL to the line pressure
during shifting at low temperatures, the engagement pressure on the
disengagement side starts actually dropping upon elapse of a
predetermined time from t1, and, at t2, the engagement pressure on
the disengagement side becomes equal to the line pressure at low
temperatures. Afterwards, the line pressure during shifting at low
temperatures is maintained.
[0277] At t3 upon elapse of a predetermined time from t1 when the
engagement order on the engagement side is issued, the engagement
pressure on the engagement side actually starts rising.
[0278] At t3 upon elapse of a predetermined timer T1 beginning with
t1 when the upshift starts, the oil pressure order for the
engagement side frictional element is minimized, ordering a
complete disengagement of the disengagement side. Afterwards, the
minimized oil pressure order continues. At t4 upon elapse of a
predetermined time from t3, engagement pressure on the
disengagement side starts dropping actually.
[0279] Because of the maximized oil pressure order issued at time
t1 when the upshift starts, the opening degree of an original port
of the pressure regulator valve 106b.about.110b is the largest. On
this account, a drop in the response characteristics of the
engagement pressure of the engagement side frictional element is
restrained even if the fluidity of working fluid drops at low
temperatures. That is to say, the time from the oil pressure order
t3 to the oil pressure rise t4 is sufficiently short so that the
outbreak of shift shocks due to delay in response of engagement
side engagement pressure may be avoided.
[0280] The unevenness of time from the oil pressure order t1 to t3
when the oil pressure rises actually is reduced because the maximum
oil pressure is ordered in succession at time t1 and
afterwards.
[0281] At t3 upon a delay of a predetermined period T1 that is
based on oil temperature from t1, an oil pressure order for the
disengagement side is issued. On this account, the outbreak of
engine race is prevented because the situation in which the
disengagement side frictional element is disengaged when the torque
capacity of the engagement side frictional element does not appear
will not happen even if time from t1 to t3 becomes long due to
response delay of the engagement side engagement pressure.
[0282] At t5 upon elapse of a predetermined time from disengagement
side engagement pressure drop t4, the disengagement side frictional
element starts slipping, and gear ratio GR starts decreasing. In
other words, inertia phase starts at t5.
[0283] At t6 upon elapse of a predetermined time from t4 when the
disengagement side engagement pressure starts dropping, the
disengagement side engagement pressure becomes zero, completing
disengagement of the disengagement side frictional element. In
addition, at t6, the engagement side engagement pressure has risen
to the neighborhood of the line pressure PL because the
predetermined time has past from t3 when the engagement side
engagement pressure started rising. Because the original pressure
port of the pressure regulator valve 106b.about.110b of the
engagement side frictional element is opened to the largest opening
degree, the ceiling of the engagement side engagement pressure is
the line pressure PL that is the original pressure.
[0284] At t7, the engagement side engagement pressure becomes as
high as the line pressure PL. On the other hand, the line pressure
PL is reduced to the line pressure during shifting at low
temperatures from t1 in succession. Therefore, the ceiling of the
engagement side engagement pressure is the line pressure during
shifting at low temperatures. Here, the line pressure during
shifting at low temperatures is set as high as an oil pressure that
is high enough to end the inertia phase so that the engagement side
engagement pressure may rise high enough to end the inertia
phase.
[0285] There is a reduction in speed at which torque capacity of
the engagement side frictional element increases owing to the
lowered ceiling of the engagement side engagement pressure, causing
a reduction in drop in engine rpm. Therefore, the outbreak of shift
shocks (jerk due to a projection in output shaft torque) is
prevented because the quantity of an increase in output torque per
a unit time becomes small.
[0286] At t8, the gear ratio GR becomes equal to a gear ratio GR2
after the upshift, ending the inertia phase. By this, the
engagement pressure control is ended, and the line pressure during
shifting at low temperatures is changed for the normal line
pressure to calculate the line pressure PL. The engagement side
engagement pressure starts rising because the ceiling of the
engagement side engagement pressure rises with a rise of line
pressure PL.
[0287] At t9 upon elapse of a predetermined time from t8, the
engagement side engagement pressure rises to the neighborhood of
the normal line pressure to secure engagement of the engagement
side frictional element.
[0288] Select Control at Low Temperatures
[0289] Referring to FIGS. 22 and 23, there is description on a
select control at low temperatures. FIG. 22 is a flow chart of a
select control at low temperatures, and FIG. 23 is its time
chart.
[0290] The flow chart shown in FIG. 22 begins with step S1 in
which, when a select performed from N range position to run range
(D range or R range) position during operation of the engine, the
inhibitor switch 45 detects the selected range position. Depending
on a kind of the selected range, the shift at low temperatures
control section 404 decides which of the frictional elements should
be hydraulically controlled as follows:
[0291] In step S10, when oil temperature detected by the oil
temperature sensor 46 is lower than a predetermined temperature,
the shift judgment at-low-temperature section 405 determines that
the current select is a select at low temperatures. After the start
of select at low temperatures, a select control at low
temperatures, which includes an engagement pressure control at low
temperatures and a line pressure control at low temperatures, is
carried out.
[0292] A1 Engagement Control
[0293] In engagement pressure control for a frictional element A1
(hereinafter, A1 engagement control), an oil pressure order for
engagement is maximized upon elapse of a predetermined timer T1
(steps S51, S52). Afterwards, the maximized engagement order
continues to be issued in succession. Here, the predetermined timer
T1 is set in response to oil temperature. In addition, in the first
embodiment, a select start is the moment upon detecting a select as
well as the moment upon maximizing an oil pressure order in an
engagement pressure control, later described, of a frictional
element A2 at low temperatures carried out simultaneously with this
detection.
[0294] After maximizing the oil pressure order for the frictional
element A1 (step S52), an inertia phase is ended when the progress
of shift SK becomes equal to or bigger than SK2 (step S53). By
this, the A1 engagement control is ended (step S53). In addition, a
backing timer T2 is monitored as the backing of the judgment of end
of A1 engagement control by the degree of shift SK so that, when
the degree of shift SK fails to satisfy the relationship SK>SK2,
the A1 engagement control is ended upon elapse of the predetermined
time t2 (step S54).
[0295] A2 Engagement Control
[0296] On the other hand, in engagement pressure control for a
frictional element A2 (hereinafter, A2 engagement control), an oil
pressure order for engagement is maximized immediately after the
start of select (step S61). This aims at completion of engagement
of the frictional element A2 earlier than the first frictional
element A1. Afterwards, the maximized order continues to be issued
in succession, and the A2 engagement control is ended.
[0297] Line pressure control at select at low temperatures is the
same as line pressure control at downshift at low temperatures and
at upshift at low temperatures. But, you use properly a map to
refer to from a line pressure map at N-D select at low temperatures
and a line pressure map at N-R select at low temperatures (see FIG.
10).
[0298] In other words, in a line pressure control at a select from
N range to D range at low temperatures, a line pressure at low
temperatures is controlled by changing, as a map to refer to, the
line pressure map at forward range for the line pressure map at N-D
select at low temperatures (step S81). When the engagement pressure
control at low temperatures is ended, the line pressure map at N-D
select at low temperatures is changed for the line pressure map at
forward range at low temperature map and the line pressure control
at low temperatures is ended (steps S82, S83, S84).
[0299] In the same way as above, in a line pressure control at a
select from N range to R range at low temperatures, a line pressure
at low temperatures is controlled by changing, as a map to refer
to, the line pressure map at forward range for the line pressure
map at N-R select at low temperatures (step S81). When the
engagement pressure control at low temperatures is ended, the line
pressure map at N-D select at low temperatures is changed for the
line pressure map at reverse range at low temperature map and the
line pressure control at low temperatures is ended (steps S82, S83,
884).
[0300] At time t1, as shown in FIG. 23, engagement of the
frictional element A2 starts by maximizing an oil pressure order
for the frictional element A2 simultaneously with detection of a
select at low temperatures. Afterwards, the maximized oil pressure
order continues to be issued in succession. Issuing the engagement
order for the frictional element A2 simultaneously with the start
of select makes it possible to complete engagement of the
frictional element A2 well before completion of engagement of the
frictional element A1, to shorten oil pressure rise time for the
frictional element A2, and to facilitate the progress of select at
low temperatures.
[0301] In addition, at time t1 when the select starts, the line
pressure PL is decreased to line pressure at select at low
temperatures, and afterwards, this decreased oil pressure is
maintained until the end of the select at low temperatures.
[0302] At t3 upon elapse of a predetermined time after t1 when the
select starts, the engagement pressure of the frictional element A2
starts rising.
[0303] At t2 upon elapse of a predetermined timer T1, an oil
pressure order for the frictional element A1 is maximized, and the
maximized order continues to be issued in succession at t2 and
onwards. In this way, by giving the oil pressure order to the
frictional element A1 upon elapse of the time T1 from t1,
simultaneous engagement of the frictional elements A1 and A2 is
prevented and the order of engagement of the frictional element A1
and engagement of the second frictional element A2 is prevented
from being mixed up by different run situations.
[0304] In other words, there is the possibility that different in
magnitude of shift shocks at a select may occur due to mixing up of
the order of engagement of the frictional element A1 and that of
frictional element A2 caused by different driving conditions. To
cope with this, the oil pressure order is given to the frictional
element A1 upon elapse of the predetermined timer T1.
[0305] For example, let us consider a select from N range to R
range at low temperatures, which engages the low & reverse
brake L&R/B and the 3-5 reverse clutch 3-5R/C.
[0306] First, let us assume that the low & reverse brake
L&R/B is selected as the first frictional element A1, and the
3-5 reverse clutch 3-5R/C as the second frictional element A2. In
this case, the 3-5 reverse clutch 3-5R/C is engaged before the low
& reverse brake L&R/B is engaged. First, rotation of the
rotary shaft S1, which turns via the torque converter 3
accompanying the engine rpm, is transmitted via the engaged 3-5
reverse clutch 3-5R/C to the rotary shaft S5 and the carrier 16,
causing them to turn. In this state, engaging the low & reverse
brake L&R/B requires the rotating rotary shaft S5 and the like
to come to a stop. Therefore, inertia energy is released from these
members by engaging the low & reverse brake L&R/B.
[0307] On the other hand, let us assume that the 3-5 reverse clutch
3-5R/C is selected as the frictional element A1 and the low &
reverse brake L&R/B is selected as the frictional element A2.
In this case, the rotation of the rotary shaft S5 is not
transmitted to the rotary shaft S5 and the carrier 16 because the
low & reverse brake L&R/B is engaged before 3-5 reverse
clutch 3-5R/C is engaged. The inertia energy of these member does
not pose any problem when, in this state, the 3-5 reverse clutch
3-5R/C is engaged. Therefore, the output shaft torque changes upon
engagement of the frictional element A1 are less in this case than
the above-mentioned case where the low & reverse brake
L&R/B is selected as the frictional element A1.
[0308] Therefore, the shift at-low-temperature control section 404
selects as the frictional element A1 the 3-5 reverse clutch 3-5R/C
and as the frictional element A2 the low & reverse brake
L&R/B, and give the oil pressure order to the low & reverse
brake L&R/B simultaneously with start of select.
[0309] At t3 upon elapse of the predetermined time after t1 when
the oil pressure order is given to the frictional element A2, the
oil pressure of the frictional element A2 starts rising actually.
In the same way, the oil pressure of the frictional element A1
starts rising actually at t4 upon elapse of the predetermined time
after t2 when the oil pressure order is given to the frictional
element A1.
[0310] The original pressure ports of the pressure regulator valves
106b.about.110b are opened to the largest degree by ordering the
maximum oil pressures at time t1 and t2. By this, actual oil
pressure rise times from t1, t2 to t3, t4 are sufficiently short
enough and a drop in response characteristic of each of the
friction elements A1 and A2 is reduced even if the fluidity of
working oil drops at low temperatures.
[0311] And, the unevenness of time from the oil pressure order t1,
t2 to the oil pressure rise t3, t4 is reduced because the maximum
oil pressure is ordered in succession at time t1, t2 and
afterwards. Moreover, outbreak of oil pressure vibrations in the
pressure regulator valves 106b.about.110b for the frictional
elements A1 and A2 is prevented.
[0312] Ceiling of each of the engagement pressure becomes equal to
the line pressure PL that is the original pressure because the
original pressure ports of the pressure regulator valves
106b.about.110b are fully opened to the largest degree. On the
other hand, the line pressure PL is lowered in succession from t1
to the line pressure at select at low temperatures. Therefore, the
ceiling of each of the frictional elements becomes equal to the
line pressure at select at low temperatures.
[0313] At t5 upon elapse of a predetermined time from t4 when the
engagement pressure of the frictional element A1 starts rising, Nt
starts varying with respect to Ne and the degree of shift SK starts
increasing. That is, the inertia phase starts at t5.
[0314] At t6, the engagement pressure of the frictional element A2
becomes equal to the line pressure at select at low temperatures.
In the same way, at t7, the engagement pressure of the frictional
element A1 becomes equal to the line pressure at select at low
temperatures.
[0315] Because the ceiling of engagement pressures of the
frictional elements A1 and A2 is lowered to the line pressure at
select at low temperatures, speed at which the torque capacity of
each of the frictional elements A1 and A2 drops and thus changes in
output torque per unit time become small. Therefore, engagement
shocks and a jerk of the vehicle body upon select operation are
prevented.
[0316] The line pressure at select at low temperatures are set high
enough to end the inertia phase so that the engagement pressure of
each of the frictional elements A1 and A2 rises high enough to end
the inertia phase.
[0317] At t8, the degree of shift SK reaches the predetermined
value SK2 which indicates end of select, ending the inertia phase.
By this, the select end judgment is made. At this moment, the line
pressure at select at low temperatures is changed for the normal
line pressure, and the engagement pressures of the frictional
elements A1 and A2 start rising.
[0318] At t9 upon elapse of a predetermined time from t8, the
engagement pressures of the frictional elements A1 and A2 rise to
the neighborhood of the normal line pressure to secure engagement
of the frictional elements.
Effects of First Embodiment
[0319] The first embodiment of a control system for automatic
transmissions has the effects listed below:
[0320] (1) As mentioned above, the first embodiment of the
automatic transmissions control system has the automatic
transmission 1 configured to achieve a shift by engaging an
engagement side frictional element and disengaging a disengagement
side frictional element. The target shift stage determination
section 401 determines whether or not there is a need for the shift
in the automatic transmission 1. The line pressure regulator valve
132b regulates line pressure by draining ejection pressure of the
oil pump O/P. The shift control section 402 controls the line
pressure regulator valve 132b. The pressure regulator valve
106b.about.110b regulates the line pressure PL to give engagement
pressure applied to the engagement side frictional element. The
shift control section 402 controls the pressure regulator valve
106b.about.110b for the engagement side frictional element. The oil
temperature sensor 46 detects oil temperature within the automatic
transmission 1. The engagement pressure at-low-temperature
regulation section gives, when oil temperature detected by the oil
temperature sensor 46 is lower than a predetermined oil temperature
and the target shift stage determination section 401 determine a
need for the shift, an order for the maximum hydraulic pressure
high enough for complete engagement to the pressure regulator valve
106b.about.110b for engagement side frictional element to start the
shift, and continues to give the order for the maximum hydraulic
pressure in succession until end of the shift.
[0321] When a shift is determined at low temperatures in which
response characteristic of hydraulic control associated with the
shift drops, an original pressure port is fully opened in degree to
decrease a drop in response characteristic of at least engagement
pressure applied to the engagement side frictional element by
giving an order for the engagement pressure to the engagement side
frictional element to start the shift by engagement pressure
at-low-temperature regulation section 406. Unevenness of time until
the engagement pressure on the engagement side starts rising is
reduced by continuing to give the order for the maximum oil
pressure in succession. Moreover, the pressure regulator valve
106b.about.110b for the engagement side frictional element is free
from fluctuations and outbreak of oil pressure vibrations is
prevented by continuing to give an order for constant oil pressure
to the pressure regulator valve in succession until the end of the
shift.
[0322] In addition, in the first embodiment, there is description
on the type in which a disengagement side friction element is
controlled by engagement pressure, but the same effects are
obtained by applying the above-mentioned technology only to the
engagement side friction element if the disengagement side friction
element is constituted by one-way clutch and the like.
[0323] (2) The pressure regulator valve 106b.about.110b regulates
the line pressure PL to give engagement pressure applied to the
disengagement side frictional element, and the shift control
section 402 that controls the pressure regulator valve
106b.about.110b for the disengagement side frictional element, and
the target shift stage determination section 401 is configured to
determine whether or not there is a need for an upshift. The
engagement pressure at-low-temperature regulation section 406
gives, when oil temperature detected by the oil temperature sensor
46 is lower than a predetermined oil temperature and the target
shift stage determination section 401 determine a need for the
shift, an order for the minimum hydraulic pressure to the pressure
regulator valve for the disengagement side frictional element upon
elapse of a first period T1 (corresponding to a first period)
beginning with the above-mentioned starting the shift (when the
order for the maximum hydraulic pressure high enough for complete
engagement to the pressure regulator valve for the engagement side
frictional element).
[0324] There is an effect that engine race caused due to delay in
response characteristic of engagement pressure applied to the
engagement side frictional element is appropriately prevented by
decreasing the engagement pressure to the disengagement side
frictional element upon elapse of the predetermined period T1 which
is based on the oil temperature at an upshift at low
temperatures.
[0325] (3) As mentioned above, the first embodiment of the
automatic transmissions control system has the automatic
transmission 1 configured to achieve a shift by engaging an
engagement side frictional element and disengaging a disengagement
side frictional element. The target shift stage determination
section 401 determines whether or not there is a need for a
downshift in the automatic transmission 1. The line pressure
regulator valve 132b regulates line pressure PL by draining
ejection pressure of an oil pump O/P. The shift control section 402
controls the line pressure regulator valve 132b. The pressure
regulator valve 106b.about.110b regulates the line pressure PL to
give engagement pressure applied to the engagement side frictional
element. The shift control section 402 controls the pressure
regulator valve 106b.about.110b for the engagement side frictional
element. The pressure regulator valve 106b.about.110b regulates the
line pressure to give engagement pressure applied to the
disengagement side frictional element. The shift control section
402 controls the pressure regulator valve for the disengagement
side frictional element. The oil temperature sensor 46 detects oil
temperature within the automatic transmission 1. The engagement
pressure at-low-temperature regulation section 406 gives, when oil
temperature detected by the oil temperature sensor 46 is lower than
a predetermined oil temperature and the target shift stage
determination section 401 determine a need for the shift
(downshift), an order for the minimum hydraulic pressure for
complete disengagement to the pressure regulator valve
106b.about.110b for the disengagement side frictional element to
start the shift, gives an order for the maximum hydraulic pressure
high enough to complete engagement to the pressure regulator valve
106b.about.110b for the engagement side frictional element upon
elapse of a predetermined period T1 (corresponding to a second
period) beginning with the starting the shift, and continues to
give the order for the maximum hydraulic pressure in succession
until end of the shift.
[0326] At a downshift at low temperatures, when a shift is
determined at low temperatures in which response characteristic of
hydraulic control associated with the shift drops, the pressure
regulator valve 106b.about.110b for the engagement side frictional
element is free from fluctuations and outbreak of oil pressure
vibrations is prevented by continuing to give an order for constant
oil pressure to the pressure regulator valve 106b.about.110b in
succession until the end of the shift. Moreover, when a downshift
is determined, the engagement pressure applied to the disengagement
side frictional element is lowered to start the shift, facilitating
the progress of the shift. Since the engagement pressure applied to
the engagement side friction element needs to rise to an oil
pressure high enough to end an inertia phase by the end of the
inertia phase, there is an effect that outbreak of interlock due to
a delay in draining hydraulic fluid from the disengagement side
frictional element is appropriately prevented by increasing
engagement pressure applied to the engagement side frictional
element upon elapse of the predetermined time T1, which is based on
oil temperature, beginning with start of the downshift.
[0327] (4) The line pressure at-low-temperature regulation section
407 gives, when oil temperature detected by the oil temperature
sensor is lower than a predetermined oil temperature and the target
shift stage determination section 401 determine a need for the
shift, an order to the line pressure regulator valve 132b for a
predetermined period beginning with the starting the shift so that
the line pressure is determined based on an input torque to the
automatic transmission and as high as the lower limit hydraulic
pressure capable of ending inertia phase.
[0328] Shift shocks are avoided because high level of line pressure
PL is prevented unaltered from being used as the engagement
pressure applied to the engagement side frictional element by the
line pressure at-low-temperature regulation section 407. That is,
immediately after start of shift resulting from judgment that the
shift is a shift at low temperatures, it is ordered to lower line
pressure PL from the level of line pressure PL during shifting at
normal temperatures to a level as high as the lower limit capable
of ending the inertia phase. The line pressure PL, which is
supplied as a source of the engagement pressure, is lowered to the
above-mentioned level and high level line pressure PL unaltered
will not be used as a source of the engagement pressure until the
engagement pressure applied to the engagement side frictional
element rises, thus restraining the rapid rise of engagement
pressure at such oil pressure in the neighborhood of the lower
limit capable of ending inertia phase. As a result, rapid shift
shocks can be avoided. First, the line pressure regulator valve
132b does not need to control anything but one quantity as compared
to the pressure regulator valves 106b.about.110b. Second, the line
pressure regulator valve 132b is always in a pressure equilibrium
state. Third, a constant oil pressure order for the line pressure
regulator valve 132b is issued for a predetermined period in
succession during shifting and the period for which the constant
oil pressure order is issued is long. Because of them, there is an
effect that the oil pressure vibrations in the line pressure
regulator valve 132b are prevented from occurring.
[0329] (5) The line pressure at-low-temperature regulation section
407 gives, when oil temperature detected by the oil temperature
sensor 46 is lower than a predetermined oil temperature and the
target shift stage determination section 401 determine a need for
the shift, an order to the line pressure regulator valve 132b for a
predetermined period (corresponding to a third period) beginning
with the starting the shift for a hydraulic pressure lower than the
line pressure that is ordered when oil temperature detected by the
oil temperature sensor 46 is equal to or higher than the
predetermined oil temperature and the target shift stage
determination section determine a need for the shift.
[0330] Shift shocks are avoided because high level of line pressure
PL is prevented unaltered from being used as the engagement
pressure applied to the engagement side frictional element by the
line pressure at-low-temperature regulation section 407. First, the
line pressure regulator valve 132b does not need to control
anything but one quantity as compared to the pressure regulator
valves 106b.about.110b. Second, the line pressure regulator valve
132b is always in a pressure equilibrium state. Third, a constant
oil pressure order for the line pressure regulator valve 132b is
issued for a predetermined period in succession during shifting and
the period for which the constant oil pressure order is issued is
long, Because of them, there is an effect that the oil pressure
vibrations in the line pressure regulator valve 132b are prevented
from occurring. Further, for the predetermined period (third
period), it is enough that the time needed to end the shift is
secured. For example, it may be a predetermined period that may be
set based on the degree of shift SK or a predetermined time
(backing timer T2) that is considered to be long enough to end the
shift.
[0331] (6) As mentioned above, the first embodiment of the
automatic transmissions control system has the automatic
transmission 1 configured to engages frictional elements A1, A2
(first frictional element) based on a lever operation from a
non-run range (P range, N range) to a run range (D range, R range
and the like). The target shift stage determination section 401
(corresponding to a lever operation detection section) detects the
lever operation based on a signal from an inhibitor switch 45. The
line pressure regulator valve 132b regulates line pressure by
draining ejection pressure of an oil pump O/P. The shift control
section 402 (line pressure regulation section) controls the line
pressure regulator valve 132b. The pressure regulator valves
106b.about.110b regulate the line pressure to give engagement
pressures applied to the frictional elements A1, A2. The shift
control section 402 controls the pressure regulator valves
106b.about.110b. The oil temperature sensor 46 that detects oil
temperature within the automatic transmission 1. The engagement
pressure at-low-temperature regulation section 406 gives, when oil
temperature detected by the oil temperature sensor 46 is lower than
a predetermined oil temperature and the inhibitor switch 45
determines the lever operation, an order for the maximum hydraulic
pressure high enough to complete engagement to the pressure
regulator valves 106b.about.110b to start the shift, and continues
to give the order for the maximum hydraulic pressure in succession
until end of the shift.
[0332] At a select at low temperatures, when a shift is determined
at low temperatures in which response characteristic of hydraulic
control associated with the select drops, an original pressure port
of the pressure regulator valve 106b.about.110b for the engagement
side friction element is fully opened in degree to start the shift
thereby to decrease a drop in response characteristic of engagement
pressure applied to the engagement side frictional element by
engagement pressure at-low-temperature regulation section 406.
Unevenness of time until the engagement pressure on the engagement
side starts rising is reduced by continuing to give the order for
the maximum oil pressure in succession. Moreover, the pressure
regulator valve 106b.about.110b for the engagement side frictional
element is free from fluctuations and outbreak of oil pressure
vibrations is prevented by continuing to give an order for constant
oil pressure to the pressure regulator valve in succession until
the end of the shift.
[0333] (7) The line pressure at-low-temperature regulation section
407 gives, when oil temperature detected by the oil temperature
sensor 46 is lower than a predetermined oil temperature and the
inhibitor switch 45 detects the lever operation, an order for
hydraulic pressure to the line pressure regulator valve 132b for a
predetermined period (a third period) beginning with start of
engagement of frictional elements A1, A2 (first frictional element)
so that the line pressure may be determined based on an input
torque to the automatic transmission and as high as the lower limit
hydraulic pressure capable of ending inertia phase.
[0334] Shift shocks are avoided because high level of line pressure
PL is prevented unaltered from being used as the engagement
pressure applied to the engagement side frictional element by the
line pressure at-low-temperature regulation section 407. That is,
immediately after start of shift resulting from judgment that the
shift is a shift at low temperatures, it is ordered to lower line
pressure PL from the level of line pressure PL during shifting at
normal temperatures to a level as high as the lower limit capable
of ending the inertia phase. The line pressure PL, which is
supplied as a source of the engagement pressure, is lowered to the
above-mentioned level and high level line pressure PL unaltered
will not be used as a source of the engagement pressure until the
engagement pressure applied to the engagement side frictional
element rises, thus restraining the rapid rise of engagement
pressure at such oil pressure in the neighborhood of the lower
limit capable of ending inertia phase. As a result, rapid shift
shocks can be avoided. First, the line pressure regulator valve
132b does not need to control anything but one quantity as compared
to the pressure regulator valves 106b.about.110b. Second, the line
pressure regulator valve 132b is always in a pressure equilibrium
state. Third, a constant oil pressure order for the line pressure
regulator valve 132b is issued for a predetermined period in
succession during shifting and the period for which the constant
oil pressure order is issued is long. Because of them, there is an
effect that the oil pressure vibrations in the line pressure
regulator valve 132b are prevented from occurring.
[0335] (8) The line pressure at-low-temperature regulation section
407 provides, when oil temperature detected by the oil temperature
sensor 46 is lower than a predetermined oil temperature and an
inhibitor switch 45 detects the lever operation, an order to the
line pressure regulator valve 132b for a predetermined period
(corresponding to a third period) beginning with the starting the
shift for a hydraulic pressure lower than the line pressure that is
ordered when oil temperature detected by the oil temperature sensor
46 is equal to or higher than the predetermined oil temperature and
the inhibitor switch 45 detects the lever operation.
[0336] Shift shocks are avoided because high level of line pressure
PL is prevented unaltered from being used as the engagement
pressure applied to the engagement side frictional element by the
line pressure at-low-temperature regulation section 407. First, the
line pressure regulator valve 132b does not need to control
anything but one quantity as compared to the pressure regulator
valves 106b.about.110b. Second, the line pressure regulator valve
132b is always in a pressure equilibrium state. Third, a constant
oil pressure order for the line pressure regulator valve 132b is
issued for a predetermined period in succession during shifting and
the period for which the constant oil pressure order is issued is
long. Because of them, there is an effect that the oil pressure
vibrations in the line pressure regulator valve 132b are prevented
from occurring, Further, for the predetermined period (third
period), it is enough that the time needed to end the shift is
secured. For example, it may be a predetermined period that may be
set based on the degree of shift SK or a predetermined time
(backing timer T2) that is considered to be long enough to end the
shift.
Other Embodiments
[0337] In the above, there is description on the best mode of
implementing the present invention along with the first embodiment,
but the present invention should not be limited to this embodiment.
The present invention includes any modifications with departing the
spirit of the invention.
[0338] For example, the present invention is applicable to an
automatic transmission having a planetary gear train and hydraulic
circuit different from those used in the automatic transmission 1
of the first embodiment. And, the predetermined timer T1 used in
the downshift control at low temperatures for an engagement side
frictional element may be triggered for up-counting by any one of a
judgment of shift and an order for the minimum hydraulic pressure
if they occur at different timings. The predetermined timer T1 used
in the upshift control at low temperatures for a disengagement side
frictional element may be triggered for up-counting by any one of a
judgment of shift and an order for the maximum hydraulic pressure
if they occur at different timings. And so in select control at low
temperatures.
General Interpreting of Terms
[0339] In understanding the scope of the present invention, the
term "comprising" and its derivatives, as used herein, are intended
to be open ended terms that specify the presence of the stated
features, elements, components, groups, integers, and/or steps, but
do not exclude the presence of other unstated features, elements,
components, groups, integers and/or steps. The foregoing also
applies to words having similar meanings such as the terms,
"including", "having" and their derivatives. Also, the terms
"part," "section," "portion," "member" or "element" when used in
the singular can have the dual meaning of a single part or a
plurality of parts. Also as used herein to describe the above
embodiment(s), the following directional terms "forward, rearward,
above, downward, vertical, horizontal, below and transverse" as
well as any other similar directional terms refer to those
directions of a vehicle equipped with the present invention.
Accordingly, these terms, as utilized to describe the present
invention should be interpreted relative to a vehicle equipped with
the present invention. The terms "detect" as used herein to
describe an operation or function carried out by a component, a
section, a device or the like includes a component, a section, a
device or the like that does not require physical detection, but
rather includes determining, measuring, modeling, predicting or
computing or the like to carry out the operation or function. The
term "configured" as used herein to describe a component, section
or part of a device includes hardware and/or software that is
constructed and/or programmed to carry out the desired
function.
[0340] While only selected embodiments have been chosen to
illustrate the present invention, it will be apparent to those
skilled in the art from this disclosure that various changes and
modifications can be made herein without departing from the scope
of the invention as defined in the appended claims. For example,
the size, shape, location or orientation of the various components
can be changed as needed and/or desired. Components that are shown
directly connected or contacting each other can have intermediate
structures disposed between them. The functions of one element can
be performed by two, and vice versa. The structures and functions
of one embodiment can be adopted in another embodiment. It is not
necessary for all advantages to be present in a particular
embodiment at the same time. Every feature which is unique from the
prior art, alone or in combination with other features, also should
be considered a separate description of further inventions by the
applicant, including the structural and/or functional concepts
embodied by such feature(s). Thus, the foregoing descriptions of
the embodiments according to the present invention are provided for
illustration only, and not for the purpose of limiting the
invention as defined by the appended claims and their
equivalents.
* * * * *